Abstract
As radiation therapy is needed by approximately 50% of patients with cancer there needs to be ongoing research to ensure that radiation therapy targets the tumour effectively and minimises potential side effects. Major advances in radiation therapy, due to improvements in engineering and computing, have made it more precise, reducing side effects and improving cancer control. Patients need to be informed of its risks, both short and long term, to enable them to be active participants in their cancer treatment path.
Keywords
Introduction
In 2005, Lee was diagnosed with a Her2-positive, grade 3 breast tumour. Her treatment consisted of AC chemotherapy (a combination of adriamycin and cyclophosphamide), a 30-cycle course of radiation therapy, and 17 cycles of a new targeted drug, Herceptin. At the multi-disciplinary team clinic, she was warned that her lungs could be burnt by the radiation, her hair would fall out, and she would need a cocktail of additional drugs to combat the nausea of chemotherapy. She knew a little about chemotherapy, but had no knowledge regarding radiation therapy. She did not receive any written information about the three treatments, nor specifics regarding therapy-induced side effects.
A few years after treatment, she started to experience late-onset side effects. One was an excruciating pain that travelled from the base of her oesophagus upwards towards the back of her throat. An endoscopic examination by a gastroenterologist revealed that her oesophagus was rigid in sections. It is believed that the stiffness was caused by the radiation therapy. Another symptom that emerged was fainting. It is believed that her heart muscle was affected by the AC chemotherapy. Adriamycin is most commonly linked to changes in the heart muscle. She undertook vascular surgery to improve blood flow to her heart. As further side effects develop, she has learnt to treat them or modify her life.
Like all cancer treatments, radiation therapy often causes side effects. These are different for each person and depend on the type of cancer, its location, the radiation dose, and the patient’s general health. Most people will have some mild side effects during and just after treatment. Three long-term side effects are: radiation-induced second malignancies; cardiotoxicity, and problems in the heart and vascular system; and radiation-induced fibrosis.
Radiation-induced second malignancies. As children and young adults are likely to survive for a longer duration after anticancer therapy, they are at a greater risk than older adults. There is a need for integrated research involving clinical studies, radiobiology, and physics to estimate and reduce the risk of treatment-related second cancers. Cardiotoxicity, and problems in the heart and vascular system. Cardiotoxicity is a risk when a large volume of heart muscle is exposed to a high dose of radiation. Patients who develop radiation-related cardiotoxicity should be under the care of a cardiologist who understands the relationship between cancer treatment and heart problems. Radiation-induced fibrosis. Fibrosis may cause the bladder to hold less urine, the breasts to feel firmer, the arms or legs to swell, breathlessness due to the lungs being less stretchy, and narrowing of the oesophagus, making it difficult to swallow. There is a real need for ongoing research to find therapies that can prevent formation of fibrosis or to treat the disease. Prevention has focused on improvements in radiation therapy technique.
The main goal of cancer treatment is to extend life, but the quality of that extended life is also important for the patient. Some patients do not care much how a treatment affects quality of life. They want to fight to get to a particular milestone, even if their quality of extra life is poor. For others, quality of life is as important as length of life, or maybe even more so.
The risks and side effects of radiation therapy need to be communicated effectively to the patient. Frequently in the culture of ‘doctor knows best’, the patient with cancer trusts their doctor to do what is appropriate and does not discuss the attendant risks. To support understanding by patients, the creation of patient-centred resources regarding radiation treatment and possible side effects is necessary. Written information allows the patient to reflect on what will be involved during the therapy, enables accurate understanding for discussion with family and friends, and becomes an excellent reference for managing both short-term and late-onset therapy-induced side effects.
1. What advances have occurred in radiation therapy?
Radiation therapy techniques have changed significantly over the past few decades, thanks to improvements in engineering and computing. Major advances in radiation therapy have made it more precise, reducing side effects and improving cancer control.
Computed tomography (CT), magnetic resonance imaging, and functional imaging such as positron emission tomography provide definitive imaging before treatment, allowing a more accurate assessment of disease spread and more effective treatment planning. Four-dimensional CT is becoming available in the clinical setting. There is integration of imaging information in every phase of treatment, from simulation to planning to delivery. Treatment imaging allows the clinician to correct for patient movement, internal organ movement, and change in tumour size, enabling personalised treatment. In addition, advancements in the treatment couch can correct for pitch, roll, and yaw, resulting in a more accurate and reliable treatment set-up. Advances in the capability of linear accelerators enable the delivery of high-dose treatment to tumour cells whilst sparing tissue that is healthy. At one time, radiation therapy was delivered in large fields with a static dose, but now intensity-modulated radiation therapy allows the radiation dose to conform more precisely to the three-dimensional shape of the tumour by modulating the radiation beams into multiple smaller beams.
2. What will radiation therapy look like in the future?
Artificial intelligence in health care will complement doctors, offering several advantages by assisting doctors to make better data-driven decisions. Artificial intelligence can help to improve the efficiency of diagnosis, management, administration, and treatment. It will improve imaging and delivery to ensure consistent treatment for all patients with cancer. Magnetic resonance linear accelerators will help to visualise and target the tumour during treatment, allowing greater precision in cancer treatment, maximising the chance of the best-possible outcome for the patient. As the human body is a dynamic system, tumours move during radiation treatment. Several solutions for real-time tumour targeting are in development. Kilovoltage intrafraction monitoring is one of the technologies being clinically pioneered in Australia to turn today’s standard linear accelerator into tomorrow’s real-time cancer targeting system. It is purely a software solution. Rethinking cancer treatment system designs with the patient experience, safety, and costs in mind may improve global access to radiation therapy. Three designs are in development at the Australian Cancer Research Foundation Image X Institute which are smaller, and cheaper to manufacture and house. Radiation therapy will be used increasingly in the oligometastatic setting, given the positive results of several clinical trials. A phase II trial found that radiation therapy can generate an immune system response that was not previously believed possible in oligometastatic prostate cancer.
As radiation therapy is needed by approximately 50% of patients with cancer at some stage in their treatment journey, there needs to be ongoing research to ensure that radiation therapy targets the tumour effectively and minimises potential side effects. It is important that patients with cancer are informed of its risks, both short and long term, along with those of other cancer therapies, to enable them to be active participants in their cancer treatment path.