Radiation therapy for bowel cancer
Also known as radiotherapy, this treatment uses a controlled dose of radiation, such as focused x-ray beams, to kill or damage cancer cells. The radiation is targeted to the specific area of the cancer, and treatment is carefully planned to do as little harm as possible to your normal body tissue near the cancer. Radiation therapy is often combined with chemotherapy (chemoradiation). This is because chemotherapy makes cancer cells more sensitive to radiation.
Learn more about:
- How radiation therapy is used
- How radiation therapy is given
- What its side effects are
- Radiation therapy’s effect on fertility and sexual function
- Video: What is radiation therapy?
Radiation therapy is not generally used to treat locally advanced colon cancer. Commonly, a short course of radiation therapy or a longer course of chemoradiation is used to shrink the tumour before surgery for locally advanced rectal cancer. The aim of this treatment is to make the cancer as small as possible before it is removed. This means it will be easier for the surgeon to completely remove the tumour and reduces the risk of the cancer coming back.
Occasionally, if the rectal cancer is found to be more advanced than originally thought, radiation therapy may be used after surgery to destroy any remaining cancer cells.
External beam radiation therapy is the most common type of radiation therapy for rectal cancer. Newer techniques deliver the dose to the affected area without damaging surrounding tissue. These improvements have reduced the side effects from radiation therapy.
During treatment, you will lie on a treatment table under a machine called a linear accelerator. Each treatment takes only a few minutes, but a session may last 10–20 minutes because of the time it takes to set up the machine.
There will be a break between radiation therapy and surgery to allow the treatment to have its full effect. If radiation therapy is given with chemotherapy, you will have it once a day for 5–6 weeks, then there will be a gap of 6–12 weeks before surgery. If radiation therapy is given by itself, you will have a shorter course, usually for five days, then a shorter gap before surgery.
For more on this, see Radiation therapy.
The side effects of radiation therapy vary. Most are temporary and disappear a few weeks or months after treatment. Radiation therapy for rectal cancer is usually given over the pelvic area, which can irritate the bowel and bladder.
Common side effects include feeling tired, needing to pass urine more often and burning when you pass urine (cystitis), redness and soreness in the treatment area, diarrhoea, constipation or faecal urgency and incontinence. Radiation therapy can cause the skin or internal tissue to become less stretchy and harden (fibrosis). It can also affect fertility and sexual function.
People react to radiation therapy differently, so some people may have few side effects, while others have more. Your treatment team will give you advice about possible side effects and how to manage them.
Radiation to the pelvic area can damage the lining of the rectum, causing inflammation and swelling (known as radiation proctitis). This can cause a range of symptoms including diarrhoea, the need to empty the bowels urgently and loss of control over the bowels (faecal incontinence). When treating rectal cancer, these side effects may appear shortly after radiation therapy, but are generally not a problem long term because the rectum is removed during surgery. Your treatment team will talk to you about your risk of developing radiation proctitis. See also some ways to cope with bowel changes.
Video: What is radiation therapy?
A/Prof Craig Lynch, Colorectal Surgeon, Peter MacCallum Cancer Centre, VIC; Prof Tim Price, Medical Oncologist, The Queen Elizabeth Hospital, Adelaide, and Clinical Professor, Faculty of Medicine, The University of Adelaide, SA; Department of Dietetics, Liverpool Hospital, NSW; Dr Hooi Ee, Gastroenterologist, Sir Charles Gairdner Hospital, WA; Dr Debra Furniss, Radiation Oncologist, Genesis CancerCare, QLD; Jocelyn Head, Consumer; Jackie Johnston, Palliative Care and Stomal Therapy Clinical Nurse Consultant, St Vincent’s Private Hospital, NSW; Zeinah Keen, 13 11 20 Consultant, Cancer Council NSW; Dr Elizabeth Murphy, Head, Colorectal Surgical Unit, Lyell McEwin Hospital, SA. We also thank the health professionals, consumers and editorial teams who have worked on previous editions.
View the Cancer Council NSW editorial policy.
Click below to download a PDF booklet on this topic.