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Abstract

Purpose. Despite mounting evidence indicating that exercise training has a positive effect on cancer recovery, the influence of cancer type on the response to exercise training remains uncharacterized. Therefore, the adaptations to exercise training were compared between groups composed of 7 different forms of cancer. Methods. A total of 319 cancer survivors completed fatigue inventories and participated in assessments of cardiorespiratory function, which encompassed aerobic capacity (VO_2peak), pulmonary function (forced vital capacity [FVC] and forced expiratory volume in 1 second [FEV₁]), and resting blood pressure and heart rate. Participants were divided into 7 groups based on cancer type, including breast cancer (BC, n = 170), prostate cancer and other male urogenital neoplasia (PC, n = 38), hematological malignancies (HM, n = 34), colorectal cancer (CC, n = 25), gynecological cancers (GC, n = 20), glandular and epithelial neoplasms (GEN, n = 20), and lung cancer (LC, n = 12). All participants completed an individualized, multimodal exercise intervention consisting of cardiorespiratory, flexibility, balance, and muscular strength training 3 days per week for 3 months. Following the intervention, all subjects were reassessed. Generalized Estimating Equations with exchangeable working correlation structure was used to model each response; the group by time interaction effect represented the effect of cancer type on exercise-associated improvements. Results. No significant (P > .05) group by time interaction effects were observed between different types of cancer for any parameter. Pre- to postexercise contrasts revealed significant improvements in VO_2peak in BC, PC, HM, and GEN at the Bonferroni adjusted significance level (.00714). Heart rate was significantly lowered in the BC and CC groups. Mean fatigue indices decreased by at least 17% in all groups, but these changes were only significant in the BC, HM, CC, and GC groups. Systolic blood pressure decreased significantly in BC and GC, and diastolic blood pressure decreased significantly only in the BC group while pulmonary function remained unchanged in all cancer types. Conclusion. Although trends toward improved cardiorespiratory and fatigue parameters only reached significance in some groups, there were no significant differences between cancer types. This suggests that cardiorespiratory and fatigue improvements following rehabilitative exercise are not dependent on cancer type. Further research investigating alternative physiological parameters are needed to confirm the relationship between cancer type and exercise-mediated rehabilitation.

Keywords

cancer treatment cancer treatment–related side effects exercise intervention individually prescribed exercise cancer type cardiorespiratory fitness fatigue

Introduction

Advances in early detection and treatment methods designed to remove, arrest, and prevent recurrence of cancer have increased long-term survival rates of individuals diagnosed with cancer. Overall death rates from cancer decreased by 20% between 1990 and 2009, accounting for the avoidance of more than 1 million deaths during this time.¹ Despite decreased mortality rates in cancer patients in recent years, side effects from surgery, chemotherapy, radiation, hormone therapy, or any combination of these cancer treatments can be detrimental to a cancer survivor’s functional capacity^2-7 and mood state.^8-11 Notably, low aerobic capacity (AC)¹² and low levels of physical activity^13,14 are associated with all-cause mortality in various cancer populations, whereas exercise may be associated with reduced risk of recurrence and cancer-related death.¹⁵ Furthermore, VO_2peak, the standard measurement of AC, is a predictor of cardiovascular disease risk and chemotherapy-induced left ventricular dysfunction in individuals with solid malignancies.¹⁶ The most frequently reported symptom in cancer survivors is cancer-related fatigue, which is defined by the National Comprehensive Cancer Network as “a distressing persistent, subjective sense of physical, emotional and/or cognitive tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and interferes with usual functioning.”¹⁷ The National Cancer Institute estimates that fatigue occurs in up to 96% of cancer survivors who have been treated for cancer,¹⁸ although some studies indicate that at least 60% of cancer patients experience fatigue.¹⁹ Considering the strong association between fatigue and patient quality of life in cancer survivors,^20,21 it is a worthwhile endeavor to implement interventions that are intended to reduce fatigue.

In order to address the deleterious side effects of cancer treatments, methods to combat the reduction in functional capacity and mood state have become a common topic of investigation. A prescribed, whole-body exercise intervention for cancer survivors is one such rehabilitation method, and has been reported to be effective at reducing levels of fatigue^10,22-24 and increasing AC^22,25-27 in various cancer populations. Exercise has been shown to improve muscular endurance and quality of life in prostate cancer survivors,²⁸ as well as AC and fatigue in females with breast cancer.²⁵ Segal et al²⁹ reported that among prostate cancer patients initiating radiotherapy, those engaged in a resistance training program reduced fatigue and improved quality of life, aerobic fitness, and strength, when compared with usual care. More recently, a meta-analysis by Fong et al²⁷ evaluated the effect of an exercise intervention in cancer survivors across 34 randomized controlled trials, and as a whole, physical activity was positively associated with improvements in AC, quality of life, body composition, and fatigue.

Cancer is not a single pathology, but rather a broad classification of many cancer types, differing by disease etiology, sites of involvement, affected patient populations, symptoms, and treatment strategies. It is possible that because of these differences, cancer type may affect exercise-mediated rehabilitation from cancer treatments. Although substantial evidence suggests that individually prescribed and supervised exercise interventions aid in the improvement of both physiological and psychological parameters in cancer survivors,^{10,23,25,28-32} the influence of cancer type on the response to exercise training has yet to be investigated. Therefore, the primary purpose of this study was to compare the changes in cardiorespiratory function (CF) and fatigue between groups with different cancer types following individually prescribed and supervised exercise training. It was hypothesized that due to the individualized nature of the exercise intervention, there would be no significant differences observed between the cancer types in response to the intervention. A secondary purpose of this study was to investigate whether supervised prescriptive exercise training could improve CF and fatigue parameters pre- to postexercise intervention within each cancer type.

Methods

A total of 319 cancer survivors participated in this study, all of whom were recovering from cancer surgery, chemotherapy, radiation treatment, hormone therapy, or a combination of these treatments. These subjects were selected from an initial pool of 709 cancer survivors who completed in an initial medical screening and fitness assessment following oncologist referral to an exercise-based cancer rehabilitation program at the Rocky Mountain Cancer Rehabilitation Institute . Individuals who had completed treatment more than 5 years at the time of this assessment were excluded, with only 16 subjects more than 36 months out of treatment. Regardless of time out of treatment, patients were referred to this cancer rehabilitation program in response to a loss of physical function associated with cancer treatment. Overall attrition rate, which included individuals who did not begin or adhere to the 3-month exercise intervention and/or did not complete a reassessment of fitness, was 52%, or a total of 370 individuals. This high attrition rate was primarily associated with the time commitment or length of the intervention, scheduling conflicts with trainers, and individual health changes (eg, cancer recurrence), rather than injury associated with the intervention. There was only 1 documented injury resulting in a subject’s withdrawal from the study (bone fracture associated with a fall in an elderly client).

The university’s institutional review board approved all study procedures. Written and verbal information pertaining to the study was given to participants in detail prior to the intervention. Medical screening and a physician directed physical examination were completed prior to assessments.

Subjects were divided into 7 groups based on their diagnosed cancer type. The groups consisted of breast cancer (BC, n = 170), prostate cancer and other male urogenital neoplasia (PC, n = 38), hematological malignancies (HM, n = 34), colorectal cancer (CC, n = 25), gynecological cancers (GC, n = 20), glandular and epithelial neoplasms (GEN, n = 20), and lung cancer (LC, n = 12). The HM group was composed of Hodgkin’s and non-Hodgkin’s lymphoma, leukemia, multiple myeloma, and myelodysplasia, while the GC group included ovarian, uterine, cervical, and endometrial cancers. The GEN group consisted of thymic carcinoma, adenocarcinoma, adenoidcystic carcinoma, neuroendocrine carcinoma, and pancreatic, thyroid, hepatic, kidney, appendix, and intestinal cancers, while male urogenital cancers also included males with testicular, penile, and bladder cancers. An additional 13 patients who completed the exercise program and fitness reassessment had cancers that did not fit within the cancer type classifications relevant to this study, and included brain cancer, sarcoma, and squamous cell carcinoma patients. The flow of patients through the study is illustrated in Figure 1. Characteristics of each group, including treatment status (during vs following treatment, time out of treatment, type of treatment) age, sex, attrition rate, and self-reported physical activity prior to cancer diagnosis are presented in Table 1.

Figure 1.

Flow of participants through the study.

Table 1.

Group Characteristics.

	Breast	Prostate	Hematological	Colon	Gynecological	GEN	Lung
Age in years (mean ± SD)	55.8 ± 10.0^a	68.1 ± 10.6	55.1 ± 15.6^a	60.3 ± 13.3	55.1 ± 9.9^a	61.4 ± 13.8	61.3 ± 14.3
Height in inches (mean ± SD)	64.0 ± 2.6^b	69.2 ± 2.9	65.8 ± 3.1^a	67.3 ± 3.4	63.9 ± 2.6^b	65.1 ± 3.5^a	63.4 ± 4.2^b
Weight in pounds (mean ± SD)	164.2 ± 35.5^a	202.9 ± 37.0	185.5 ± 48.6	182.1 ± 46.3	163.0 ± 40.5^a	186.0 ± 50.8	159.5 ± 48.4^a
BMI in kg/m² (mean ± SD)	28.3 ± 6.3	29.8 ± 5.6	30.8 ± 5.5	30.6 ± 5.8	30.3 ± 6.0	30.2 ± 6.5	30.0 ± 6.7
Female (%)	100	0	73.5	52.1	100	70	58.3
Attrition rate (%)	53.7	44.1	44.3	45.7	56.5	53.5	70.0
In treatment (%)	20.6	22.5	19.4	18.5	20.0	20.0	7.7
Months out of treatment^c (mean ± SD)	6.0 ± 8.1	17.6 ± 22.6	10.0 ± 15.4	10.2 ± 12.0	11.1 ± 17.6	11.6 ± 14.4	9.5 ± 16.1
Treatment history (%)
Surgery	98.2	63.9	85.3	72.7	63.2	73.7	83.3
Chemotherapy	58.8	38.9	63.6	78.3	73.7	75.0	83.3
Radiation	14.4	34.3	8.9	18.2	15.8	15.0	16.7
Physically active prior to cancer diagnosis	52.1	59.5	55.9	47.6	56.3	47.4	66.7

Abbreviations: BMI, body mass index; GEN, glandular and epithelial neoplasms; CC, colorectal cancer; PC, prostate cancer and other male urogenital neoplasia.

Significantly different than PC.

Significantly different than PC and CC (P < .05).

Excludes individuals currently undergoing treatment.

Physical Fitness Assessment

Following an initial review of medical and cancer history and a physical examination by the clinic’s medical director, certified cancer exercise specialists conducted a comprehensive assessment of CF, which included tests of AC, pulmonary function (PF), and resting measurements of heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP). For the assessment of AC, subjects performed a Bruce Treadmill Protocol to volitional fatigue in a dedicated cancer rehabilitation facility. The medical director was present at the time of treadmill testing for all subjects with moderate or high cardiovascular risk in accordance with guidelines set forth by the American College of Sports Medicine.³³ Additionally, blood pressure, HR, rating of perceived exertion (RPE), and oxygen saturation (SaO₂) were monitored throughout the progression of the graded exercise test. Aerobic capacity was expressed as VO_2peak, which was determined using a Bruce Treadmill Protocol–specific prediction equation. To evaluate test reliability and objectivity for assessment procedures, a subset of 15 participants was reassessed by a different cancer exercise specialist the following week, yielding a reliability coefficient of r = 0.92. Expired gas analysis was used during one of these assessments to validate VO_2peak values derived from the prediction equation. There was no significant difference (P = .98) between VO_2peak achieved using gas analysis compared to values determined by the prediction equation.

Pulmonary function was assessed using a Flowmate Plus electronic spirometer (Spirometrics Inc, Gray, ME), which recorded forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁). The participant’s measured result was compared to the predicted normal for FVC and FEV₁ based on the participant’s age, sex, and height to obtain a percentage of the predicted value (%pred). PF is expressed as percentage of predicted, and classified as low (<75%), low limit of normal (75% to 80%), within normal limits (81% to 94%), or excellent (95%). HR, DBP, and SBP were recorded with the participant in a seated position prior to the assessment, following several minutes of quiet sitting.

Psychological Assessment

Psychological parameters were assessed using inventories designed to measure fatigue in cancer patients. Fatigue was determined using the behavioral/severity, affective, sensory, cognitive/mood, and total fatigue scores from the Piper Fatigue Scale.^34,35 This consists of 22 items numerically scaled 0 to 10 that measure the 4 dimensions of subjective fatigue as well as total fatigue. The behavioral fatigue subscale included 6 questions and was used to assess the impact of fatigue on school or work, interacting with friends, and the overall interference with activities that are enjoyable. The affective fatigue subscale included 5 questions and was used to assess the emotional meaning attributed to fatigue. The sensory fatigue subscale included 5 questions and was used to assess the mental, physical, and emotional symptoms of fatigue. The cognitive/mood fatigue subscale included 6 questions and was used to assess the impact of fatigue on concentration, memory, and the ability to think clearly. The average score on 22 total questions from the subscales provided the total fatigue score.

Exercise Intervention

Following completion of the initial fitness assessment, an individualized exercise prescription was developed. Each participant then completed a 3-month exercise intervention where he or she trained individually with a cancer exercise specialist 3 days per week. Each 1-hour session was in accordance with the participant’s prescribed intensity and training modalities, based on their assessment results. Exercise sessions varied depending on the participant’s health and fitness status, but typically included a 5-minute warm-up, 20 minutes of aerobic exercise, 25 minutes of resistance training, and 10 minutes of flexibility and balance training. Blood pressure and HR were measured at the beginning and end of the exercise session, and HR, RPE, and SaO₂ were monitored throughout. Aerobic exercise intensity was based on the survivors’ initial VO_2peak, and was generally low to moderate intensity, ranging from 30% to 60% of heart rate reserve (HRR). The Karvonen or percentage heart rate reserve method was used to determine exercise heart rate intensity using the formula (exercise target heart rate = [(220 − age) − resting heart rate] × percent of exercise intensity + resting heart rate). Subjects with poor overall health status health or low fitness were initially prescribed an intensity level of 30% to 45% HRR or a RPE of 1 to 3, whereas subjects who are already active, have a moderate health status, or average fitness began their aerobic exercises at 50% to 60% of HRR or an RPE of 4 to 5. The mode of aerobic exercise selected for each participant was based on the mode offering the greatest anticipated benefit. Options included outdoor or treadmill walking, stationary cycling, recumbent stepping, or walking on an Aquaciser underwater treadmill. Although rate of progression varied significantly by subject, cancer exercise specialists aimed to increase speed or resistance weekly, while keeping RPE values less than 5 and HR values less than 75% HRR.

In addition to parameters evaluated in this study, a battery of 7 muscular strength measurements (predicted one-repetition maximum [1-RM]) were used to allow for appropriate prescription of resistance exercise. At the beginning of the intervention, initial percentage of 1-RM corresponded with the percentage of HRR values for aerobic exercise, based on initial health and fitness status (30% to 45% 1-RM for low fitness, 50% to 60% for average fitness). Cybex Eagle selectorized strength machines (Cybex International Inc, Medway, MA), free weights, resistance bands and body weight exercises were all used for the exercise intervention, depending on fitness, mobility, and comfort of the cancer patient. Muscular endurance was emphasized over hypertrophic training, as subjects performed 8 to 15 repetitions per set and typically ended each set at muscular fatigue rather than muscle failure. Resistance was increased when 8 to 15 repetitions no longer resulted in muscular fatigue.

On completing the 3-month intervention, all subjects were reassessed for PF (FVC and FEV₁), AC (VO_2peak), and resting HR, SBP, and DBP. In addition, all subjects completed the fatigue inventory at the conclusion of the exercise intervention.

Statistical Analyses

Data are presented in Tables 1 and 2 as means ± SD. The effect of supervised exercise training was determined by evaluating cardiorespiratory fitness and fatigue changes pre- to postexercise intervention using generalized estimating equations with exchangeable working correlation structure, controlling for sex, age, time out of treatment, type of treatment, body mass index, and prior exercise habits. The effect of cancer type on exercise-associated improvements was determined with the group by time interaction effect. Family significance was set at a probably of .05, with a Bonferroni adjusted significance level of α = .00714 used for each of the post hoc within-group contrasts. Statistical analyses were performed using SAS Version 9.3 (SAS Institute, Cary, NC).

Table 2.

Cardiorespiratory Function and Fatigue Before (Pre) and After (Post) a 3-Month Exercise Intervention.^a

		Cancer Type
Variable	Time Point	Breast	Prostate	Hematological	Colon	Gynecological	GEN	Lung
n		170	38	34	25	20	20	12
VO_2peak (mL/kg/min)	Pre	22.3 ± 6.4	22.4 ± 7.7	19.1 ± 6.0	23.4 ± 5.5	23.0 ± 6.4	19.5 ± 4.8	17.8 ± 7.7
VO_2peak (mL/kg/min)	Post	25.3 ± 6.3^b	25.5 ± 6.3^b	23.1 ± 5.6^b	25.4 ± 5.2	25.8 ± 5.6	25.4 ± 7.9^b	19.6 ± 7.6
Resting heart rate (bpm)	Pre	85.1 ± 13.4	78.4 ± 13.2	86.9 ± 16.0	83.7 ± 13.3	85.4 ± 13.8	82.2 ± 14.2	88.8 ± 11.8
Resting heart rate (bpm)	Post	81.5 ± 12.6^b	74.2 ± 10.9	80.5 ± 13.7	74.8 ± 8.9^b	83.6 ± 14.2	74.1 ± 13.2	87.0 ± 12.8
Systolic BP (mm Hg)	Pre	125.3 ± 16.6	132.3 ± 13.2	122.0 ± 14.4	121.8 ± 10.6	122.4 ± 18.7	131.6 ± 16.6	126.6 ± 19.1
Systolic BP (mm Hg)	Post	120.9 ± 12.8^b	127.4 ± 15.3	121.4 ± 16.1	122.6 ± 10.9	116.2 ± 12.0^b	124.6 ± 18.0	123.6 ± 12.7
Diastolic BP (mm Hg)	Pre	78.4 ± 9.1	79.2 ± 8.4	76.5 ± 11.0	75.0 ± 8.2	75.7 ± 10.1	79.1 ± 7.9	79.9 ± 8.5
Diastolic BP (mm Hg)	Post	75.0 ± 8.3^b	75.0 ± 9.0	74.5 ± 9.2	74.0 ± 8.4	74.9 ± 8.4	76.1 ± 8.2	75.3 ± 10.0
FVC (%pred^c)	Pre	101.4 ± 19.8	102.7 ± 21.9	97.1 ± 15.5	98.6 ± 16.4	103.4 ± 15.0	96.2 ± 19.7	84.4 ± 27.3
FVC (%pred^c)	Post	102.3 ± 17.5	102.4 ± 20.3	100.3 ± 22.5	102.4 ± 16.7	104.5 ± 16.0	94.2 ± 19.3	85.8 ± 22.7
FEV₁ (%pred)	Pre	97.2 ± 21.1	97.3 ± 22.9	90.4 ± 21.6	91.6 ± 23.3	94.5 ± 22.1	87.0 ± 23.4	75.9 ± 29.3
FEV₁ (%pred)	Post	98.4 ± 19.0	96.8 ± 23.1	90.5 ± 15.6	96.3 ± 19.9	100.1 ± 17.4	87.2 ± 23.7	76.3 ± 26.3
Fatigue	Pre	4.9 ± 2.2	3.9 ± 2.3	5.0 ± 2.3	4.2 ± 2.5	5.1 ± 1.4	4.6 ± 2.4	5.4 ± 2.4
Fatigue	Post	3.6 ± 2.2^b	3.3 ± 2.3	3.4 ± 2.4^b	2.5 ± 1.9^b	3.4 ± 2.0^b	3.4 ± 2.2	4.0 ± 2.7

Abbreviations: BP, blood pressure; GEN, glandular and epithelial neoplasms; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 second.

Values are expressed as mean ± SD.

Post is significantly different from Pre (Bonferroni-corrected P < .0071).

Percentage of predicted based on age, sex, and height.

No time by cancer group interaction effects were observed.

Results

Initial characteristics of study participants are listed in Table 1. The proportion of females differed by cancer type as, by definition, the PC group had no females while the BC and GC groups consisted of only females. The other cancer groups tended to have more female participants, ranging from 52% to 74% of the subpopulations. The PC group was significantly older and heavier (P < .05) than the BC, HM, and GC groups, but there were no other age or weight differences. When accounting for sex-related height differences by evaluating body mass index, there were no significant differences in body composition between the groups. All 319 subjects completed both pre- and postintervention physical fitness assessments, while only 277 of these subjects completed both pre- and postintervention fatigue instruments, with the BC group accounting for nearly all of these missing values.

Combined pre- and postintervention CF and fatigue means for all groups are presented in Table 2. Generalized estimating equations revealed no significant group by time interaction effects between different types of cancer for any parameter (P > .05). Pre- to postexercise contrasts revealed significant improvements (P < .001) for the breast cancer group in VO_2peak (13.3%), resting HR (−4.2%), fatigue (−25.6%), SBP (−3.4%), and DBP (−4.3%). The prostate cancer group had a statistically significant improvement in VO_2peak (13.9%, P = .0034), but there were no other significant differences in this group.

The HM group improved in VO_2peak (20.9%, P < .001) and fatigue parameters (−33.0%, P < .001), while the CC group improved in HR (−10.6%, P < .001) and fatigue (−35.5%, P < .001). Improvements in fatigue (34%, P < .001) were significant in the GC group, whereas the GEN group improved in VO_2peak (30%, P < .001). This latter group had the largest absolute (5.9 mL/kg/min) and relative (30.1%) gains in VO_2peak. All nonsignificant changes in VO_2peak, HR, and fatigue trended toward improvements, whereas the nonsignificant changes in PF did not. Most, but not all, SBP and DBP values revealed a pattern of improvement, although only SBP in GC and both BP parameters in the BC group improved significantly (P < .001).

Discussion

Despite differing etiologies, sites of involvement, patient populations, symptoms, and treatment strategies between different cancer types, limited research has examined the role of cancer type in the effectiveness of exercise in cancer rehabilitation. Durak et al³⁶ examined the benefits of a 20-week exercise intervention in prostate cancer patients and carcinoma/leukemia patients. The carcinoma/leukemia group showed greater improvements in strength (52% vs 38% average increase), aerobic capacity (51% vs 5%), and quality of life, but no between-group analyses were performed and the groups varied markedly by age (71 vs 45 years), initial health status, and years since diagnosis. A 2011 meta-analysis by Jones et al,²⁶ revealed a 2.91 mL/kg/min weighted mean difference in VO_2peak in cancer patients who had participated in an exercise intervention versus those who had not. Of the 6 studies included in this analysis, 3 investigated the effect of exercise in only breast cancer patients, 1 included breast and colon, and the others involved prostate and lymphoma patients, respectively. Although these studies all indicated an improvement in VO_2peak, comparison between cancer groups would be imprudent because of differences in the length and nature of exercise interventions. Hsieh et al³⁷ a found that a moderate intensity, multimodal exercise program was effective at improving cardiopulmonary function and fatigue within a single cancer type (breast cancer), regardless of treatment type.

Oldervoll et al³⁸ emphasized the lack of research on exercise and cancer rehabilitation in cancer groups other than breast and prostate, and called for more specific analyses of exercise interventions among varying cancer types as they relate to cancer rehabilitation. There is evidence that exercise as a preventative measure is more protective against the development of certain cancer types than others,³⁹ but similar data concerning cancer rehabilitation is currently sparse. Therefore, the purpose of this investigation was to determine if cancer type influences the effectiveness of an individualized, 3-month exercise intervention as a means of physical and psychological rehabilitation in cancer patients.

The current study showed no significant differences between cancer groups from pre- to postintervention in any CF or fatigue parameters. The BC groups improved significantly in all parameters except PF, whereas the LC group trended toward improvement in all but the pulmonary parameters, although these improvements did not reach significance. It should be noted that despite these somewhat divergent responses, there was no time by cancer type interaction effect between these groups. For instance, percentage changes in VO_2peak (13.3% vs 10.2%), HR (−4.2% vs −2.1%), and fatigue (25.6% vs 25.4%) were very similar between the BC and LC groups respectively, but a smaller sample size in LC likely affected the power for the within group analysis. These data suggest that although exercise training helped to improve many physiological and psychological parameters, the responses were not specific to cancer type. It would therefore be appropriate to prescribe exercise interventions to cancer patients based on individual needs, without a particular emphasis on cancer type.

Changes in CF and fatigue were uniform across cancer groups despite substantial differences in initial means for several variables. For instance, although the LC group began with very low pulmonary function values (84% and 76% of predicted values for FVC and FEV₁, respectively) exercise-associated improvement was not statistically divergent from other groups. In fact, pre- to postexercise contrasts indicated no change in pulmonary function for any group, but considering the low to moderate intensity of aerobic exercise during the intervention, this is not surprising. Previous research has indicated that pulmonary function does not improve with aerobic exercise in either older obese men⁴⁰ or in healthy individuals with specific inspiratory muscle training,⁴¹ indicating a lack of pulmonary plasticity in both healthy and unhealthy populations. Furthermore, other than FEV₁ values in the GEN and LC groups, and FVC in LC patients, all pulmonary function values were classified as “excellent” prior to the exercise intervention.

Significant improvements in cardiorespiratory fitness were revealed in 4 groups. Despite a lack of statistical significance, the CC, GC, and LC groups trended toward improved aerobic capacity, with 8.9%, 12.2%, and 10.2% increases, respectively. These data do not vary significantly from previous literature. Courneya et al⁴² showed no significant difference in improvement in treadmill time in colorectal cancer survivors who engaged in an at-home exercise program versus those who did not, despite a 60-second greater improvement in treadmill time in the exercise group. Alternately, a recent pilot study in ovarian cancer patients indicated a 22% increase in VO_2peak following a 12-week, home-based exercise intervention, and by 6 months, there had been a 28% improvement (P = .008).⁴³ The lack of significance in the LC group may have been because of limitations associated with low pulmonary function, but results from this study are similar to a 2008 study by Jones et al,⁴⁴ which indicated a similar and significant improvement (11.3%, P = .008) in VO_2peak. The general improvement in cardiorespiratory fitness in the current study is consistent with the literature.^{25,26,30,37,45} Mean improvements in VO_2peak for all groups was 3.24 mL/kg/min, which comports well with the 2.91 mL/kg/min improvement reported in the previously mentioned meta-analysis.²⁶

Fatigue failed to improve significantly in the PC, GEN, and LC groups, but much like VO_2peak values, all groups demonstrated a trend toward improvement. Apart from the PC group, mean fatigue scores dropped by at least 25%, but large within-group variations (±1.4% to ±2.7%) in fatigue severity prevented these reductions from reaching significance in these 3 groups. The PC group had a 17% reduction in fatigue, but this was the only group with initial fatigue values in the “mild” severity classification (1.0-3.9 out of 10), whereas the remaining groups were initially classified as “moderate” severity (4.0-6.9 out of 10). It could be argued that this reflects less room for improvement in the PC group rather than a poor response to the exercise intervention. Following the exercise intervention, all but the LC groups fell within the mild fatigue classification. The results from the current study were in concordance with a meta-analysis by Brown et al,²⁴ which showed a significant reduction in fatigue following exercise interventions in both BC and PC populations, but nonsignificant reductions among leukemia, lymphoma, and CC groups. Because of differences in length and modality of intervention, a direct analysis of the time by group effect on fatigue was not feasible.

In the current study, only the BC group had significant reductions in diastolic blood pressure, but 2 groups (HM and LC) had greater mean reductions in DBP (−4.2 and −4.6 mm Hg, respectively). Likewise, only BC and GC has significant SBP reductions, but other groups (PC, GEN) had similar mean reductions (−4.9 and −7.0 mm Hg, respectively). Like with fatigue values, large within-group variances were present in both SBP (±10.6 to ±19.1 mm Hg) and DBP (±7.9 to ±11.0 mm Hg). Daily variations in BP related to diet, sleep patterns, hydration, stress level, and changes in medication may be associated with this substantial within group variability. A meta-analysis investigating the effect of exercise interventions on blood pressure in the noncancer population revealed an overall reduction of 3.84 and 2.58 mm Hg in SBP and DBP, respectively (<.001), but only 20 of 53 studies showed a significant reduction in SBP, while 16 of 50 trials resulted in significant reduction in DBP.⁴⁶

There are a few limitations of this study that must be addressed. Because a preponderance of our subjects are BC survivors and some cancer groups, particularly lung cancer (n = 12), have small sample sizes, the results of this study may inappropriately imply a less robust effect of exercise in these groups. Additionally, this study only included data for CF and fatigue parameters and therefore cannot be generalized to every aspect of cancer rehabilitation. Our group is currently investigating the effect that cancer type has on changes in muscular strength and endurance, flexibility, and quality of life in response to an exercise intervention. It may also be inappropriate to generalize these results to other exercise interventions, particularly those which are home based and not individually tailored to each patient. Finally, this study had no sedentary controls, because of the fact that our program was developed with the intention of providing exercise to all individuals seeking a rehabilitative intervention. Individuals who did not adhere to the exercise program rarely returned for a reassessment of fitness and therefore could not comprise a natural control group. It should be noted that previous studies have indicated that exercise improves fitness significantly compared to a control group. For instance, the 2011 meta-analysis by Jones et al²⁶ demonstrated that usual care resulted in a significant reduction (−1.02 mL/kg/min) in VO_2peak, whereas an exercise intervention was associated with a significant increase (2.91 mL/kg/min) in VO_2peak.

Conclusions

To our knowledge, no previous investigations have directly compared the impact of cancer type on the effectiveness of an exercise intervention as a means of cancer rehabilitation. The results of this investigation indicate that the exercise-mediated improvements in cardiorespiratory fitness and fatigue are generally not affected by cancer type, despite differing etiologies, symptoms, target tissues, patient populations, and treatment strategies. Additionally, several CF and fatigue parameters improved from pre- to postexercise intervention within each cancer type. Strategies to reduce or reverse the damaging effects of cancer treatment need to reflect individual patient needs without a particular emphasis on cancer type. Although these data indicate that an individualized moderate-intensity exercise intervention during or following cancer treatment is an effective method of improving CF and reducing fatigue regardless of cancer type, further studies investigating additional parameters and exercise strategies are warranted.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Cancer Type Does Not Affect Exercise-Mediated Improvements in Cardiorespiratory Function and Fatigue

Abstract

Keywords

Introduction

Methods

Physical Fitness Assessment

Psychological Assessment

Exercise Intervention

Statistical Analyses

Results

Discussion

Conclusions

Footnotes

Declaration of Conflicting Interests

Funding

References

Supplementary Material