Integrating Dietary Supplements Into Cancer Care

Abstract

Many studies confirm that a majority of patients undergoing cancer therapy use self-selected forms of complementary therapies, mainly dietary supplements. Unfortunately, patients often do not report their use of supplements to their providers. The failure of physicians to communicate effectively with patients on this use may result in a loss of trust within the therapeutic relationship and in the selection by patients of harmful, useless, or ineffective and costly nonconventional therapies when effective integrative interventions may exist. Poor communication may also lead to diminishment of patient autonomy and self-efficacy and thereby interfere with the healing response. To be open to the patient’s perspective, and sensitive to his or her need for autonomy and empowerment, physicians may need a shift in their own perspectives. Perhaps the optimal approach is to discuss both the facts and the uncertainty with the patient, in order to reach a mutually informed decision. Today’s informed patients truly value physicians who appreciate them as equal participants in making their own health care choices. To reach a mutually informed decision about the use of these supplements, the Clinical Practice Committee of The Society of Integrative Oncology undertook the challenge of providing basic information to physicians who wish to discuss these issues with their patients. A list of leading supplements that have the best suggestions of benefit was constructed by leading researchers and clinicians who have experience in using these supplements. This list includes curcumin, glutamine, vitamin D, Maitake mushrooms, fish oil, green tea, milk thistle, Astragalus, melatonin, and probiotics. The list includes basic information on each supplement, such as evidence on effectiveness and clinical trials, adverse effects, and interactions with medications. The information was constructed to provide an up-to-date base of knowledge, so that physicians and other health care providers would be aware of the supplements and be able to discuss realistic expectations and potential benefits and risks.

Introduction

Dietary supplements (DS) are one of the most easy to access complementary and integrative therapies. Use of DS is increasingly common among the US adult population. More than 40% used supplements in the 1988 to 1994 period, and more than one half of the population used them in 2003 to 2006. ¹ In 2010, it was estimated that the sale of all US herbal DS exceeded $5.2 billion. ²

Many studies confirm that the majority of patients undergoing cancer therapy also use self-selected forms of complementary therapies, including DS.^3-5 Compared with healthy populations, cancer patients appear to be more frequent users of DS.^5,6 Previous reports estimate that these products are used by 20% to 55% of cancer patients.^7-11 In more recent reports of women with breast cancer undergoing treatment and up to 9 years postdiagnosis, DS use ranged from 67% to 87%.^5,12 Patients may take DS to reduce side effects and organ toxicity, to protect and stimulate immunity, or to prevent further cancers or recurrences. Patients often do not report their use of supplements to their provider.^13,14 As a result, there is a gap in communication between the providers and their patients.

This gap in communication may result from (a) patients’ perception that their physicians are indifferent or negative toward complementary therapies or (b) physicians’ emphasis on scientific studies and evidence-based medicine, rather than patient preferences, in the selection of such therapies.^14,15

The failure of physicians to communicate effectively with patients on complementary and integrative medicine topics may result in a loss of trust within the therapeutic relationship, and in the selection by patients of harmful, useless, or ineffective and costly nonconventional therapies when effective integrative interventions may exist. Poor communication may also lead to diminishment of patient autonomy and self-efficacy and thereby interfere with the healing response.^14-17 Although scientific and evidence-based thinking is fundamental to contemporary medical practice, failure to recognize that patients often do not reason in this way interferes with the physician’s ability to address the unspoken needs of the patient with cancer. Psychological, social, and spiritual dimensions of care may be ignored if the physician cannot adapt to the individual needs of the patient or provides care without sensitivity. Particularly when physicians are faced with a question regarding an unfamiliar complementary therapy, they may feel “de-skilled” by being forced outside their zone of comfort and competence. This discomfort can lead to defensiveness and a breakdown in communication with the patient. In contrast, the physician who is receptive to patient inquiries and aware of subtle, nonverbal messages can create an environment of safety in which a patient feels and is protected and can openly discuss potential integrative medicine choices.^16-18

The physician faces multiple questions and challenges in approaching a patient with cancer who is using DS; the most important issues should be safety and efficacy.^14,19 Often, no adequate studies of a particular supplement have been published. If no safety issues are documented, and there are clinical clues that suggest possible effectiveness, should we discourage the patient from using those supplements despite the limited evidence? Even though we try to base our work on reliable scientific evidence, one cannot overlook the patient perspective in this equation. Patients frequently see natural product consumption as an avenue that they can use to empower themselves, attempt to take control of their health, and increase their quality of life.^17,18,20 Many believe that the physician has limited knowledge on supplements or has no interest in discussing the topic; as a result, most patients do not consult with their physician prior to their decision to use these supplements.^9,21

However, some patients expect their physician to study the appropriate use of the supplements that are specific to their situation, so they can obtain educated advice and cooperation in decision making. ²⁰ If their physician is not a responsive and reliable source of information, patients obtain and collect information on supplements from a variety of sources, such as advice from friends and relatives, nonprofessional literature, popular magazines, journals, daily newspapers, the Internet, advertisements, and other information provided at the health food store. At times this information is not accurate and occasionally it may even be dangerous. ²²

To be open to the patient’s perspective, and sensitive to his or her need for autonomy and empowerment, physicians may need a shift in their own perspectives. Today’s informed patients truly value physicians who appreciate them as empowered participants in making their own health care choices. The physician or other health care provider is an informed intermediary, an expert guide, a consultant. Ultimately, the patient must be encouraged and supported to make his or her own choices, informed by the best knowledge of the doctor. Perhaps the optimal approach is to discuss both the facts and the uncertainty with the patient, in order to reach a mutually informed decision. ²³

In 2009, The Society of Integrative Oncology (SIO) came up with a set of guidelines for integrating complementary medicine into cancer care. ²⁴ One of the recommendations related to the use of nutritional supplements:

For cancer patients who wish to use nutritional supplements, including botanicals for purported antitumor effects, it is recommended that they consult a trained professional. During the consultation, the professional should provide support, discuss realistic expectations, and explore potential benefits and risks. It is recommended that use of those agents occur only in the context of clinical trials, recognized nutritional guidelines, clinical evaluation of the risk/benefit ratio based on available evidence, and close monitoring of adverse effects.

To reach a mutually informed decision about the use of these supplements, the Clinical Practice Committee of the SIO took the challenge of providing basic information to physicians who wish to discuss these issues with their patients. Members of that committee, clinicians, and researchers got together to address this need. The clinicians are all members of the SIO, and have extensive experience in integrating supplements to patients affected by cancer and actually provide consultations to patients about this use.

The process of selecting the leading 10 supplements involved the following steps:

1. Each clinician in this project was requested to construct a list of supplements that they tend to use frequently in their practice

2. An initial list of close to 25 supplements was constructed. This list included supplements that have suggestions of some possible benefit and likely to carry minimal risk in cancer care.

3. From that long list, the group agreed on the 10 leading supplements that have the best suggestions of benefit.

4. Each participant selected 1 to 2 supplements that they have interest and experience in their use and wrote a manuscript related to the selected supplement in a uniformed and agreed format. The agreed format was constructed to provide a base of knowledge, so physicians and other health care providers would be able to discuss realistic expectations and potential benefits and risks with patients and families that seek that kind of information.

5. The revised document was circulated among participants for revisions and comments.

In the following pages, we provide the final document that resulted from this process as mutually agreed among the participants about these 10 leading DS.

Curcumin

Background

Curcumin (diferuloylmethane) is the major component of the Indian spice turmeric (Curcuma longa). It is found in just about every dish in India and is used as a coloring and flavoring additive in many foods. It has attracted interest because of its anti-inflammatory and chemopreventive activities. Epidemiological evidence indicates that the incidence of certain cancers is less in people who consume curcumin than in those who do not. Basic science research and observational and clinical studies demonstrated that curcumin has some activity against cancer, as well as other inflammatory conditions.^25,26

Mechanism of Action in Cancer

Curcumin has been shown to prevent a large number of cancers in animal studies. Laboratory data indicate that curcumin can inhibit tumor initiation, promotion, invasion, angiogenesis, and metastasis.^27-31

Curcumin has been shown to interfere with multiple cell signaling pathways, including cell cycle (cyclin D1 and cyclin E), apoptosis (activation of caspases and downregulation of antiapoptotic gene products), proliferation (HER-2, EGFR, and AP-1), survival (PI3K/AKT pathway), invasion (MMP-9 and adhesion molecules), angiogenesis (VEGF), metastasis (CXCR-4), and inflammation (NF-κB, TNF-α, interleukin [IL]-6, IL-1, COX-2, and 5-LOX). ³²

Curcumin also acts as a chemosensitizer and radiosensitizer for tumors in some cases. Curcumin has also been shown to protect normal organs such as liver, kidney, oral mucosa, and heart from chemotherapy- and radiotherapy-induced toxicity. ³³

The activity of curcumin reported against leukemia and lymphoma, gastrointestinal cancers, familial polyposis, pancreatic cancer, genitourinary cancers, breast cancer, ovarian cancer, head and neck squamous cell carcinoma, lung cancer, melanoma, neurological cancers, and sarcoma reflects its ability to affect multiple targets.^32-36

Safety and Side Effects

Curcumin has been used for centuries as a spice and food additive with minimal adverse effects, and the FDA is considering it as a GRAS (Generally Recognized as Safe) supplement. ³⁷

Curcumin may cause an upset stomach, especially in high doses or if given over a long period of time. ³⁸

Patients with gallbladder problems should be cautioned about the use of curcumin due to the fact that curcumin is capable of contracting the gall bladder and might exacerbate gall bladder disease. ³⁹

Historically, curcumin has been considered safe when used as a spice in foods during pregnancy and breastfeeding. However, curcumin has been found to cause uterine stimulation and to stimulate menstrual flow, and caution is therefore warranted during pregnancy. Animal studies have not found curcumin taken by mouth to cause abnormal fetal development. ⁴⁰

Dosage

There is no clear recommendation for curcumin dosage. In clinical trials, dosage has reached 12 g with no major side effects, but it seems from recent clinical trials that to obtain a clinical effect 500 to 3000 mg is sufficient. Taking the epidemiological data from India, the use of the spice is averaging around 5 g (equals to 150-250 mg of curcumin).

Curcumin has poor bioavailability due to its rapid metabolism in the liver and intestinal wall. To increase the availability, some suggest combining the use with piperine, which improves this bioavailability considerably. ⁴¹ Consuming curcumin with meals increases its absorption, especially with fatty foods such as olive oil, avocado, fish oil, milk, seeds, and so on.

Interactions

Based on laboratory and animal studies, curcumin may inhibit platelets in the blood and increase the risk of bleeding caused by other drugs, such as aspirin, anticoagulants, antiplatelet drugs, and nonsteroidal anti-inflammatory drugs. ⁴² The same caution should be applied to combining curcumin with herbs such as Ginkgo biloba, garlic, saw palmetto.

Caution should be used if curcumin is combined with cyclophosphamide and camptothecin due to possible interaction and reduction of apoptosis. ⁴³

Glutamine

Background

Glutamine is an essential amino acid that has biologic functions including gastrointestinal (GI) cell growth and regeneration. Glutamine is a precursor for glutathione and regulates intracellular redox reactions. It is essential during metabolic stress and injury and metabolized via splanchnic tissue, lymphocytes, kidney, and the liver to glutamate and ammonia. ⁴⁴

Mechanism of Action in Cancer Care and Clinical Trials

Glutamine may be useful in the oncologic setting as it has been shown to reduce cytokine production and improve the GI tract mucosal barrier. In various cancer patients undergoing chemotherapy and radiation, when glutamine was added to their treatment, there was decreased rates and severity of mucositis, neuropathy, and intestinal toxicity.^44,45 Additional benefit was observed in decreased use of pain medication in patients suffering from stomatitis, with improved nutrition, as a result of this intervention.^46,47

Glutamine may be promising for the treatment of chemotherapy-induced peripheral neuropathy possibly via upregulation of nerve growth factor. A recent study of glutamine (10 g PO TID) in breast cancer patients receiving dose dense taxane-based chemotherapy demonstrated reduced frequency of moderate to severe numbness in the glutamine versus nonglutamine group (P = .016) and a trend toward reduced moderate to severe paresthesias. ⁴⁸

Another study tested 30 g oral supplementation of glutamine in colon cancer patients receiving oxaliplatin-based chemotherapy and found a lower percentage of chemotherapy-induced peripheral neuropathy in the glutamine group after 4 cycles of treatment versus the control (no supplementation), respectively (P = .05). ⁴⁹

Safety and Side Effects

There is need for caution in patients with hepatic and renal impairment. Frequency of adverse reactions has not been defined but side effects, which are rare, include edema, headache, fever, pain, rash, abdominal pain, flatulence, nausea, vomiting, arthralgia, flu-like syndrome, and vomiting.

Dosage

It is commonly used in the powder form to produce oral solution, the dosage in that form is 10 g TID (range = 5-30 g/d). The supplement can be given orally, with enteral formula, or via feeding tube. It also may be given with meals or snacks.

Interactions

Glutamine might decrease the effectiveness of lactulose. The aforementioned trials have not noted that glutamine decreases the effectiveness of chemotherapeutic agents; however, research is inconclusive. Glutamine may interact with antiseizure medications.

Vitamin D

Background

Vitamin D is a vitamin with hormone-like action that controls calcium, phosphorus, and bone metabolism. It is the only vitamin that the body can manufacture from sunlight. An increasing proportion of the world’s population is becoming deficient in vitamin D because of indoor living, clothing customs, heliophobia, and sunscreen use. ⁵⁰ The first suggestion that vitamin D was related to cancer risk came from an observation that colon cancer mortality rates were lower in the southwestern United States compared with the northeast.^51,52 Subsequent studies have supported the finding that lower serum 25-hydroxyvitamin D levels are associated with increased risks of breast and prostate as well as colorectal and possibly other cancers, although the data are considered inconclusive.^53-55 An increasing body of evidence suggests that lower serum levels are also related with poorer prognoses in patients diagnosed with various malignancies. ⁵²

Mechanism of Action in Cancer Care and Clinical Trials

The mechanistic explanation for the protection of vitamin D and its metabolites against cancer is unclear at present but an area of tremendous ongoing research. The 25-hydroxyvitamin D metabolite, 1, 25-dihydroxyvitamin D, is the biologically active moiety that works through the vitamin D receptor to regulate gene transcription.^51,56,57 Administration of vitamin D analogues produce antiproliferative effects, can activate apoptotic pathways, and inhibit angiogenesis. Additional benefits of vitamin D may be by way of enhancing of the anticancer effects of cytotoxic agents. Other chemoprotective mechanisms by which vitamin D may work include enhancing DNA repair, antioxidant protection, and immunomodulation. One randomized trial of calcium and vitamin D conducted in Nebraska demonstrated that supplementation reduces all-cancer risk in postmenopausal women. ⁵⁸ A meta-analysis that included 2 additional randomized studies suggested that high dose (1000 IU/d) vitamin D supplementation can not only reduce the risk of total cancer but also found that higher 25-hydroxyvitamin D concentrations might be associated with increased risk of cancer. ⁵⁹

Safety and Side Effects

Vitamin D supplementation is generally safe with few side effects, most commonly gastrointestinal. In one large study of vitamin D and calcium supplementation, an increased risk of renal and urinary stones was noted. ⁵⁹ Excess vitamin D supplementation can lead to hypercalcemia. ⁵⁰

Dosage

Measurement of serum 25-hydroxyvitamin D level should guide dosing. ⁶⁰ The Institute of Medicine guideline that a level greater than 20 ng/mL is adequate for maintaining bone health may not be appropriate in the care of patients with malignant diagnoses although conclusive evidence of the optimal 25-hydroxyvitamin D level in these patients is lacking. ⁶¹ A safe recommendation would be to achieve a 25-hydroxyvitamin D level in the 40 to 80 ng/mL range. Although some food products (eggs, fortified dairy, mushrooms, and fish) may provide small amounts of vitamin D₂ (ergocalciferol), ultraviolet light from the sun is the best source of vitamin D₃ (cholecalciferol), but its production is impaired with age, obesity, and pigmentation. Hence, oral supplementation is advised. Vitamin D is a fat-soluble vitamin, so a liquid or gel-bead preparation will lead to maximal absorption. In severe deficiency, each 1000 IU dose increment should increase 25-hydroxyvitamin D levels by 10 ng/mL, decreasing as optimal levels are achieved. ⁶²

Interactions

There are no reported interactions between vitamin D supplements and individual antineoplastic agents. ⁶³ Vitamin D is metabolized by the cytochrome P450 hepatic enzyme system so theoretical interactions are possible. Concurrent use with bisphosphonates may have added benefit in increasing bone density. Through its immunomodulatory effects, vitamin D could theoretically interfere with immunosuppressants.

Maitake Mushrooms

Background

Medicinal mushrooms have a long history of use, especially in Asia where hot water fractions (decoctions and essences) are used for treating a number of conditions.^64-66 Most Basidiomycetes mushrooms contain biologically active polysaccharides in their fruit bodies, culture mycelia, or culture broth. Mushroom polysaccharides exert their antitumor action by activation of the host immune response. The mushroom β-glucans, resembling bacterial cell walls, complex with complement on macrophages and activate an immune response leading to release of various cytokines that are active in tumor inhibition.^67,68 An intact T-cell immune system is essential for the antitumor activity of medicinal mushrooms. Grifola frondosa (Maitake) is an edible soft-fleshed polypore extensively used in traditional Asian medicine for numerous health-promoting purposes. The Maitake D-fraction, a bioactive extract, is a protein-bound polysaccharide (proteoglucan) that has been most widely studied as an adjunct to conventional radiation and chemotherapy.^66,69,70 Whether the “pharmaceuticalization” of single bioactive substances is preferable to the potential synergistic interaction of the many constituents of the whole mushroom or crude extracts has not been established. ⁶⁵ Interest in the West in the investigation of medicinal mushrooms as potential anticancer agents was piqued by epidemiological studies from Japan and Brazil suggesting that long-term exposure to local medicinal mushroom species was associated with lower cancer mortality rates.^64,65

Mechanism of Action in Cancer Care and Clinical Trials

The presumed mechanism of action of the Maitake mushroom has been assumed to be that of a biologic response modifier, providing T-cell dependent immune enhancement and activation that enhanced antitumor effect. A carefully conducted phase I/II study investigating immune outcomes detected both immune stimulation and inhibition in a battery of tests. ⁶⁶ When Maitake D-fraction was given to patients receiving chemotherapy for a number of different cancers, response rates reportedly increased from 12% to 28%. ⁶⁷ Various chemotherapy side effects were also said to be ameliorated in patients receiving Maitake D-fraction. In the absence of toxicities, it is felt to be a useful adjuvant to chemotherapy. There are also reports of synergy when used with vitamin C as suggested by in vitro and animal model studies. ⁶⁶ A recent study suggests a direct antitumor effect of Maitake D-fraction with induction of apoptosis observed in breast cancer cell lines. ⁷⁰

Safety and Side Effects

The Maitake mushroom is edible and generally regarded as safe. There are no reported side effects of the mushroom extracts or the Maitake D-fraction.^66,71 As Maitake may lower blood sugar, it should be used with caution in patients with diabetes on hypoglycemic agents with careful monitoring of glucose levels while a stable dose is being established. Because of immune modulating effects, both stimulation and suppression, some integrative oncologists are reluctant to recommend medicinal mushrooms to patients with lymphoproliferative disorders until further studies have been conducted.

Dosage

A safe and effective dose has not been established.^66,70 The manufacturer’s recommended dose should be followed. Although the Maitake D-fraction has been most widely studied, numerous unfractionated whole mushroom preparations are also available.

Interactions

No known interactions are reported. Caution is advised with concurrent diabetes therapies as Maitake may have a hypoglycemic effect. As an adaptogen, Maitake may act as an immune stimulator and/or an immune suppressant, so care should be used in patients on immunomodulatory therapies. Maitake may increase the effect of antineoplastic therapies as an adaptogen, immunostimulant, or by inducing tumor cell apoptosis.

Fish Oil

Background

Fish oil supplements contain oils from cod, krill, menhaden, salmon, sardines, and other species that are high in long-chain polyunsaturated fatty acids. The omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, are most abundant. Fish oils are given in capsules, as part of oral nutritional supplements, or in parenteral or enteral forms.

Mechanism of Action and Clinical Trials

Epidemiological studies do not show that fish intake reduces cancer risk; several factors may mask this effect including cooking methods and dietary omega-6 fatty acids. ⁷² A randomized trial observed reduction of rectal polyps in familial adenomatous polyposis by fish oil. ⁷³ Fish oil may affect cancer cachexia by inhibiting proinflammatory cytokines that contribute to the acute phase protein response and consequent muscle degradation. ⁷⁴ Multiple studies of fish oil have shown mixed results in maintaining weight and lean body mass in advanced cancer patients. ⁷⁵ Recent studies in patients with earlier stage cancers, especially those receiving chemotherapy or chemoradiation, have shown beneficial effects on body weight and quality of life.^76,77 Fish oil also reduces inflammation through changes in membrane fluidity, cell signaling, and production of anti-inflammatory eicosanoids and resolvins. ⁷⁸ These effects may retard cancer progression. Two studies in prostate cancer paired fish oil with low-fat diets. The interventions reduced prostate-specific antigen levels, delayed need for conventional treatment in a watchful waiting population, and reduced Ki-67 proliferation index.^79,80 A third study found no difference on rates of postsurgical biochemical failure in Japanese prostate cancer patients. ⁸¹ Fish oil may increase apoptosis and decrease resistance by suppressing NF-κB. ⁸² Higher rates of response and clinical benefit with a tendency toward longer survival were observed in lung cancer patients supplemented with fish oil during chemotherapy, with no increase in dose-limiting toxicities. ⁸³ Fish oil improved neutrophil number and function during chemotherapy, and reduced weight loss. ⁸⁴

Finally, fish oil is used as perioperative immunonutrition—enteral supplements containing fish oil with arginine and other nutrients have been found to reduce hospital stays and postoperative complications.^85,86

Dosage Safety and Side Effects

Dosing in clinical studies is 2 to 3 g per day. Bloating, loose stools, fishy aftertaste, and eructations are the most commonly observed toxicities at these levels; enteric coating of capsules reduces them. High vitamin A levels and environmental contaminants are concerns that are typically addressed in processing; fish oil is also easily oxidized and is often formulated with antioxidants. Fish oil may increase bleeding time, although observational studies of patients using fish oil before surgery do not observe clinical concerns.^87,88

Interactions

Anticoagulant/antiplatelet drugs

Caution and monitoring should be exercised while supplementing patients on anticoagulant/antiplatelet drugs with vitamin A, especially at doses higher than 3 g per day.

Chemotherapy-induced thrombocytopenia

Because of the risk of increased bleeding tendency, some clinicians suggest holding fish oil administration during chemotherapy for patients with platelet levels below 50,000.

Antihypertensive drugs

Clinicians need to be aware that fish oil has hypotensive effects and may accentuate the effect of antihypertensive medications.

Green Tea (Camellia sinensis)

Background

Green tea consists of unfermented Camellia sinensis tea leaves with a high polyphenol content, 40% of which is epigallocatechin gallate (EGCG).

Mechanism of Action and Clinical Trials

Green tea has multiple mechanisms of action including pro-apoptotic effects, inhibition of NF-κB and other signaling molecules, ⁸⁹ antimetastatic, ⁹⁰ and prooxidative and antioxidative effects. In lab studies, it enhances activity of some chemotherapy agents. ⁹¹

Clinical trials in prostate cancer suggest that green tea may be more effective in early than later-stage conditions^92,93; short-term administration before prostatectomy suggests favorable chemopreventive effects.^94,95 Premalignant oral lesions are suppressed by green tea supplements. ⁹⁶ Positive effects were shown for a topical preparation in human papilloma virus–infected cervical lesions. Breast cancer patients drinking green tea had improved high-density lipoprotein cholesterol and nonsignificant improvements in insulin resistance and weight. ⁹⁷ Asymptomatic early stage patients with chronic lymphocytic leukemia received high-dose Polyphenon E in a phase I trial; improvements in absolute lymphocyte count and adenopathy as well as one partial remission were observed. ⁹⁸

Safety and Side Effects

For preparations that contain caffeine, caffeine-related side effects are observed, including increased gastric acidity, effects on blood glucose, and elevated catecholamine levels. For caffeinated and decaffeinated green tea and supplements, several incidents of liver toxicity have been observed, although prevention of liver disease has been observed in epidemiological studies. ⁹⁹ Clinical studies have reported grade 1 transaminitis ⁹⁸ ; low-grade gastrointestinal toxicity has also been reported. A canine study suggested that taking green tea supplements on an empty stomach increased toxicity, although bioavailability was also enhanced. ⁹⁹ Liver enzymes should be monitored in patients taking high-dose green tea supplements.

Interactions

Anticoagulants

Theoretical concerns and a case report suggest that large quantities (about 1 gallon/day) of green tea may antagonize warfarin, perhaps due to vitamin K content. ¹⁰⁰ Green tea also has antiplatelet activity.

Bortezomib

In vitro and in vivo testing suggest that EGCG could inhibit activity of bortezomib in multiple myeloma (for which bortezomib is approved). ¹⁰¹ However, in vivo testing found this effect only at unrealistically high concentrations in an experimental prostate cancer model. ¹⁰² Still with that concern in mind, some clinicians suggest to consider caution about the combined use of green tea and bortezomib.

Cytochrome P450 isoform 3A4 (CYP450 3A4)

High dose of green tea may inhibit CYP450 3A4, and one case of clinically significant interaction with tacrolimus has been reported. Based on human trials, beverage use and low-dose supplements (<800 mg/d) are found unlikely to affect this enzyme. ¹⁰³

Hepatotoxic drugs

Liver enzymes must be monitored more closely due to potential hepatotoxicity. ⁹⁹

P-glycoprotein

EGCG inhibits P-glycoprotein and may cause interaction with irinotecan or verapamil; it prolongs the half-life of irinotecan, potentially enhancing both activity and adverse potential.^104,105

Sunitinib

A case and laboratory study suggests a possible interaction between green tea and sunitinib. ¹⁰⁶

Tamoxifen

Green tea may increase tamoxifen bioavailability. ¹⁰⁷

UGT (uridine 5′ diphospho-glucuronosyltranferase) substrates

Green tea may increase side effects of drugs metabolized by this enzyme due to increased exposure. ⁹⁹

Milk Thistle

Background

Milk thistle, Silybum marianum, is a plant whose fruit and seeds have been used for more than 2,000 years as a treatment for liver and biliary disorders as well as for protection from hepatotoxins. The most active compounds found in extracts of milk thistle are flavonoids and flavonolignans, which may be found in the dried milk thistle seeds. Silymarin, a complex of flavonolignans and one flavonoid, constitutes 65% to 80% of milk thistle extracts. ¹⁰⁸

Mechanism of Action in Cancer

Clinical trials of silymarin have been conducted primarily in patients with either hepatitis or cirrhosis. ¹⁰⁹ Silymarin is the only known drug effective in protection from Amanita phalloides toxin, which targets the liver.^110,111

Three case reports,^112-114 3 pharmacokinetic studies,^115-117 and 2 double-blind randomized trials^118,119 have been conducted with varying degrees of scientific rigor. In the only report describing the use of silymarin (450 mg/d) for the treatment of hepatocellular carcinoma, the authors reported spontaneous regression of the tumor in the absence of initiation of anticancer therapy. ¹¹² In a double-blind, placebo-controlled randomized trial, 50 children who were undergoing treatment for acute lymphoblastic leukemia and who had chemotherapy-related hepatotoxicity were given silymarin (80-360 mg/d) for a 30-day period. ¹¹⁸ The treatment group had a significantly lower aspartate aminotransferase and a trend toward a significantly lower alanine aminotransferase. Vidlar et al ¹¹⁹ explored the effect of milk thistle (570 mg) in combination with selenium on quality of life, lipid profile, oxidative stress, and testosterone levels. Thirty-seven men who underwent radical prostatectomy were randomized to milk thistle and selenium or placebo for a 6-month period. The authors reported significant improvements in quality of life and lipid panel (total cholesterol and low-density lipoproteins); however, no effect was observed on measures of oxidative stress or testosterone levels. No adverse events were reported.

Safety and Side Effects

Milk thistle may be safely administered with drugs that are substrates for CYP450 3A4 and UDP glucuronosyltransferases isoform 1A1 (UGT1A1). ¹¹⁷ However, the safety of this combination may be dose dependent. A phase I study found that doses of ≤13 g are likely safe but higher doses may inhibit UGT1A1. ¹¹⁵ Hoh et al ¹¹⁶ explored the role of silibinin in 24 patients with colorectal carcinoma who were administered a daily dose of 360, 720, or 1440 mg of silibinin for 7 days before surgery. No adverse events were associated with silibinin at any of the dose levels.

Dosage

There is no clear recommendation for milk thistle dosage. An average of 200 to 400 mg per day in divided doses has been used in most of the studies investigating silymarin for hepatic disorders and antilipidemic effects. Teas made from the crushed seed are used for mild gastrointestinal upset; however, because of its lipophilic properties only a small percentage of silymarin is found in aqueous solution. Daily doses ranging from 2 to 13 g are safe. ¹¹⁵

Interactions

Two studies have evaluated the combination of milk thistle with irinotecan. Irinotecan is a substrate for many enzymes that are involved in the metabolism of many classes of chemotherapy agents. van Erp et al investigated the interaction between milk thistle (200 mg, 3 times per day) and irinotecan in 6 patients undergoing treatment for cancer. ¹¹⁷ No adverse events or altered pharmacokinetics were found.

Astragalus membranaceus

Background

The root of Astragalus membranaceus (aka Radix astragali, milk vetch, or huang qi in Chinese) is commonly used in traditional Chinese medicine herbal formulations. It is thought to have tonifying properties that “strengthen Qi (energy)”. It is used as a supportive agent during cancer treatment, and data from clinical studies suggest that it may be beneficial when used in conjunction with chemotherapy. ¹²⁰

Major constituents of astragalus include triterpenoid saponins (cycloastragenol, astragaloside I to VIII, and cyclocanthoside), cycloartane triterpene, polysaccharides, isoflavonoids, and amino acids. ¹²¹ Astragalus demonstrated immunomodulatory properties in laboratory studies, which may be responsible for its in vivo effects.

Mechanism of Action

The polysaccharides in astragalus were found to potentiate the immune-mediated antitumor activity of IL-2 in vitro, ¹²² improve lymphocyte responses in both healthy subjects and cancer patients, enhance natural killer (NK) cell activity in healthy subjects, potentiate activity of monocytes, ¹²³ and increase phagocytosis perhaps by regulating tumor necrosis factor (TNF) production. ¹²⁴ The saponins potentiate NK cell activity and restore steroid-inhibited NK cell activity in vitro. They also increase phagocytosis and demonstrate hepatoprotective effects on chemical-induced liver injury in vitro ¹²⁵ and in vivo. ¹²⁶

Astragalus has been reported to have direct anticancer effects: Astragalus extracts inhibit tumor growth, ¹²⁴ delay chemical-induced hepatocarcinogenesis in rats, ¹²⁶ have antiangiogenic property, ¹²⁷ and may also enhance the effects of platinum-based chemotherapy. ¹²⁰

Clinical Trials

There have been many studies of astragalus related to cancer treatment. Astragalus tends to be well tolerated, and preclinical studies support the immunomodulatory activities of astragalus extracts. Quite a few randomized controlled trials have also been conducted to compare the combination of astragalus with chemotherapy versus chemotherapy alone. Beneficial effects were observed. However, current evidence is not conclusive because of the low quality of the studies. The majority of the clinical trials were conducted in China using multiherb formulas that contain astragalus as the major component.

A meta-analysis of 45 randomized controlled trials suggests benefits of astragalus-based treatments for hepatocellular cancers, but the quality of the original reports was poor. ¹²⁸

Another meta-analysis was conducted in the setting of platinum-based chemotherapy for advanced non-small-cell lung cancer. Thirty-four randomized studies involving 2815 patients were analyzed. Results suggest that when used in conjunction with platinum-based chemotherapy, astragalus-based medicine improved survival, tumor response, performance status, and reduced chemotherapeutic toxicity when compared with chemotherapy alone. However, the quality of the original trials is not high, and the results are, therefore, not conclusive. ¹²⁰

In a Cochrane systematic review, 4 clinical trials were included to assess the effectiveness of astragalus on the quality of life, side effects of chemotherapy, and on adverse effects in colorectal cancer patients. A reduction in nausea and vomiting along with a decrease in the rate of leucopenia and an increase in T-lymphocytes were observed in the astragalus group compared with those treated with chemotherapy alone in the 3 studies, or with other Chinese herbal formulas in the fourth study. A major limitation of this review is that it includes only 4 studies and that the studies are of poor quality. ¹²⁹

Safety and Side Effects

Astragalus is well tolerated. Adverse effects have not been reported.

Dosage

Astragalus is frequently used as a component of a multiherb formulation. The amount of raw herb required to make the formulation varies between 10 and 90 g. It is unclear what the optimal dose is when only the astragalus extract or when a major constituent is used.

Interactions

Because of its immunomodulatory effects, astragalus may antagonize the effects of immunosuppressants such as tacrolimus and cyclosporine. It was reported to reduce immunosuppression following cyclophosphamide treatment and potentiate tumoricidal activity of aldesleukin (IL-2).^123,130,131 Astragalus should not be used in patients who are on immunosuppressants.

Melatonin

Background

Melatonin is the hormone secreted from the pineal gland following synthesis from tryptophan. Interest in melatonin for cancer therapy followed single institution reports of improved survival. Subsequent randomized trials and meta-analyses suggest a role for melatonin in the management of oncologic disease, although much of the data comes from basic science research.^132,133

Melatonin secretion correlates with circadian rhythms and sleep patterns and shows decline with age. Melatonin regulates a number of physiological functions, including growth hormone production, stimulation of apoptosis, upregulation of antioxidant enzymes, suppression of tumor and endothelial growth factors, and downregulation of pro-oxidative enzymes.^132-134

Melatonin activity at physiologic levels suppresses tumor cell proliferation and at higher levels is cytotoxic. Supplemental melatonin is effective in improving sleep for individuals with delayed sleep phase. Of epidemiologic interest is the relationship between nocturnal light exposure (third-shift workers) and reported increased incidence of breast cancer and colon cancer. Shift work is now recognized as a probable carcinogen by the International Agency on Research on Cancer.^135-138

Mechanism of Action

Melatonin levels are low during the day and rise in the early evening in response to dimming light and darkness, thereby cueing the mind and body to rest and hence the concerns about activities, which interrupt sleep cycling and sleep–darkness correlation. Melatonin has been postulated to play a key role in increased breast cancer among those with nocturnal light exposure.

Multiple mechanisms have been postulated and identified to explain these observations. Several of the previously mentioned physiologic functions regulated by melatonin are tumor suppressive. Other mechanisms under study, which affect breast tumor growth and are modulated by melatonin, include interference of estrogen synthesis by melatonin and action on estrogen receptors as a selective estrogen enzyme modifier.^139-141

Safety and Side Effects

Two recent meta-analyses have indicated improved survival at 1 year among cancer patients using melatonin as adjuvant. Wang et al ¹⁴² pooled data from 8 randomized controlled trials comparing melatonin (20 mg) concurrently administered with chemotherapy and/or radiotherapy to conventional therapy alone. Complete and partial remission rates were 32.6% (melatonin arm) versus 16.5% (conventional therapy arm; P < .00001) with a 1-year survival rate of 52.2% (melatonin) versus 28.4% (control; P < .001). The melatonin group reported less thrombocytopenia, neurotoxicity, and fatigue. Seely et al ¹⁴³ reviewed 21 clinical trials of solid tumors comparing conventional treatment with and without adjuvant melatonin. The meta-analysis reported pooled relative risk of 1-year mortality at 0.63 (95% confidence interval = 0.53-0.74; P < .001). The data suggest that melatonin can be used safely with benefit and without adverse impact on conventional therapy outcomes.^142,143

Dosage

Common sleep supplement dosages range from 0.5 to 3 mg daily with dosages of up to 20 mg daily used in solid tumor adjuvant therapy. The melatonin dosage referenced in previous studies was 20 mg.

Interactions

Cautions in the use of melatonin include the possibility of CYP1A2 and CYP2C9 metabolized drug interactions. Melatonin may theoretically affect glucose tolerance and anticoagulant pharmacology. Many substances and medications endogenously suppress melatonin production including caffeine, alcohol, nonsteroidal anti-inflammatory drugs, beta-blockers, benzodiazepines, diuretics, and calcium channel blockers. Luvox has been shown to significantly increase bioavailability of exogenous melatonin when taken concurrently.^144-147

Probiotics

Background

Probiotics are live microorganisms that, when administered in adequate amounts, are intended to have a health benefit on the host. These microorganisms exist in the body and have immune modulating properties. They affect gut mucosal maintenance, dietary nutrient absorption, and defense against exogenous bacterial pathogens. There is some evidence that the use of probiotics may be of benefit in the prevention and treatment of antibiotic associated diarrhea, infectious diarrhea, irritable bowel syndrome, Helicobacter pylori, Clostridium difficile, and others.^148-170

Use in Cancer Care and Clinical Trials

The main use of probiotics in cancer care is in the treatment of intestinal toxicity during both chemotherapy and radiation.^162-169 Colorectal cancer patients receiving one of two 5-flurouracil chemotherapy regimens were randomized to receive either Lactobacillus rhamnosus GG or guar gum. Subjects receiving the probiotic had fewer episodes of high-grade diarrhea and less abdominal discomfort. They also needed less hospital care and had fewer reductions in chemotherapy dose related to bowel toxicity. There was no toxicity associated with the Lactobacillus therapy. ¹⁶² Similar findings were found in 206 subjects receiving abdominal and pelvic radiation combined with probiotics. ¹⁶³ A larger cohort of subjects (n = 490) who underwent adjuvant postoperative radiation therapy after surgery for sigmoid, rectal, or cervical cancer were assigned to either the high-potency probiotic preparation or placebo. ¹⁶⁵ Treated subjects showed a lower incidence of radiation-induced diarrhea (32% vs 52%; P < .001), less severe high-grade diarrhea (1% vs 33%; P < .001), and less bowel movements (15 vs 5; P < .05). Again, the therapy was well tolerated. In another study, patients with locally advanced cervical cancer receiving radiation therapy combined with live Lactobacillus acidophilus plus Bifidobacterium bifidum reduced the incidence of radiation-induced diarrhea and the need for antidiarrheal medication. Of the 63 patients enrolled, grade 2 to 3 diarrhea was observed in 45% of the placebo group (n = 31) and 9% of the study drug group (n = 32; P = .002). Antidiarrheal medication use was significantly reduced in the treatment group (P = .03). The patients in the study drug group had a significantly improved stool consistency (P < .001). ¹⁶⁶

Safety and Side Effects

There are no known safety issues with most probiotic bacteria at appropriate doses in healthy people, but some people occasionally notice a temporary increase in digestive gas. Some raise theoretical concerns about the possibility of sepsis from probiotic use in patients with grade 2 or higher neutropenia. But in a study with a group of 11 patients undergoing chemotherapy and taking probiotics, tolerance of the probiotic was excellent, even though some of the patients developed grade 3/4 neutropenia secondary to the chemotherapy. ¹⁷⁰

On the other hand, a report from Spain about 3 cases of fungemia with Saccharomyces cerevisiae revealed that the only identified risk factor for that infection was treatment with a probiotic containing Saccharomyces boulardii, probiotics that are commonly used in Europe for the treatment and prevention of Clostridium difficile–associated diarrhea. The authors concluded that probiotics should be carefully used, particularly in immunosuppressed or critically ill patients. ¹⁷¹

Patients should be aware that any lactose fermenting probiotics (eg, Lactobacilli and Bifidobacterium) can potentially contain residual milk proteins and be allergenic.

Dosage

The types and number of organisms taken as probiotics depend on their intended use. In the case of chemotherapy-induced diarrhea, a dose of 10 to 20 billion cells of Lactobacillus GG (Culturelle) daily has shown to be effective. ¹⁶²

Interactions

At the time of writing this article, there are no known clear interactions with conventional cancer treatments and probiotic species. There is a theoretical concern that probiotic efficacy might be reduced when taken at the same time as antibiotics. So it is suggested by some practitioners that patients take probiotics at least 2 hours after antibiotics to maintain efficacy of both. Others express caution about taking iron supplementation simultaneously with probiotics as iron may hinder probiotic growth. ¹⁷²