Radiation Therapy for Rectal Cancer: Benefits & Side Effects

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What is Rectal Cancer?

Colorectal cancer is considered to be the second most common cause of cancer-related deaths in the United States. But while the incidence of cancer of the colon has remained steady for years, that of rectal cancer has been seen to be on the rise, especially in younger people. It is possible that the incidence of the disease is under reported, because its most common presenting symptom, rectal bleeding, is often mistakenly attributed to hemorrhoids.

Rectal cancer affects the lower end of the large intestine, or the colon, so that malignancies in these areas are often referred to as colorectal cancer. The disease may start from benign (non-malignant, non-life threatening) new growths in the walls of the large intestine known as polyps and later develop into malignancy which is invasive, aggressive and life threatening.

The cause of colorectal cancer is unknown although many risk factors have been linked to it such as:

  • Race – it affects more Jews and African Americans
  • Age – it affects mostly people over the age of 50
  • Family history of inflammatory bowel syndrome and colorectal cancer predisposes one to have the disease
  • Personal history of inflammatory bowel syndrome and diabetes type II increase risk to the malignancy
  • Obesity, diets rich in red meat and processed foods, mostly grilled and broiled foods and lack of fiber in the diet
  • Other lifestyle factors such as tobacco smoking, alcohol consumption, sedentary lifestyle, working night shifts

Rectal cancer may start from a polyp or an abnormal cell growth on the wall of the rectum which may take several years to develop into a malignancy. Symptoms usually start from constipation to changes in the size of stools and rectal bleeding. These are usually disregarded until they become prominent and are associated with abdominal pain, abdominal distension, diarrhea and weight loss. Because of this the disease may be diagnosed late, especially if screening is not done early in people who are at risk.

If the tumor remains confined to an area in the lower intestine, surgery may be able to remove the tumor. However, if the cancer cells have invaded surrounding organs, lymph nodes and have traveled even to distant sites such as the liver and bones, surgery alone cannot treat the disease.

Other therapeutic modes may be necessary in addition to surgery. These include chemotherapy, radiation therapy, immunotherapy and targeted therapy.

Benefits of Radiation Therapy for Rectal Cancer

Radiation therapy is a mode of treatment of cancer that uses high energy rays or particles to target cancer cells. Methods of applying radiation vary. External beams may be applied to destroy the malignant cells or radioactive material may be applied internally to organs or blood vessels near the affected organs.

Radiotherapy for rectal cancer is often done in advanced cases, where surgery alone cannot treat the disease, such as when the tumor is too big or has invaded other organs. Sometimes the tumor aggressively traverses the walls of the rectum and adheres to surrounding tissues, including the lymph nodes. In these cases, radiation can decrease the size and extent of the tumor, after which surgery may be done. Risk of scarring is further decreased by radiation.

Aside from facilitating surgical removal of the tumor, radiation can also prevent future recurrence of the tumor.

Radiation is also an option for patients who are too sick to undergo immediate surgery. It decreases symptoms like internal bleeding, pain and the effects of intestinal obstruction thus helping to prepare the patient for future surgery.

Radiation is best used with chemotherapy in some cases, especially when the cancer has widely spread.

Risks of Radiation Therapy

Like other modes of therapy radiation has its side effects such as:

  • External beams can cause skin irritation on the site where they pass
  • Nausea
  • Weakness
  • Radiation can affect surrounding organs like the bladder, causing frequency in urination, bloody urine and pain during urination
  • The rest of the bowels may also be affected and cause incontinence, diarrhea, painful bowel movements, bloody stools
  • Sexual problems for men include impotence in men and vaginal irritation in women


American Cancer Society, “Colorectal Cancer” accessed 12/10/10


WebMD, “Rectal Cancer on the Rise in Young People” accessed 12/10/10