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Colon and rectal cancers - Radiation

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of colorectal cancer.

Alternative Names

Colorectal cancer

Radiation:

Radiation therapy uses x-rays to kill cancer cells that might remain after an operation or to shrink large tumors before an operation so that they can be removed surgically. The object of radiation therapy is to damage the tumor as much as possible without harming surrounding tissues. Radiation may be administered in one of the following two ways:

Externally from a source outside the body, such as a linear accelerator (external beam radiation)
Internally through small radioactive pellets implanted directly into the tumor (brachytherapy)

Preoperative and Postoperative Radiation with Chemotherapy

The main use for radiation therapy in people with colon cancer is when the cancer has attached to an internal organ or the lining of the abdomen. When this occurs, the surgeon cannot be certain that all the cancer has been removed, and radiation therapy may be used to kill any cancer cells remaining after surgery. Radiation therapy is seldom used to treat metastatic colon cancer because of side effects, which limit the dose that can be used.

For rectal cancer, radiation therapy is usually given to help prevent the cancer from coming back in the pelvis where the tumor started. It may be given either before or after surgery, but recently doctors have begun to favor preoperative treatment, along with chemotherapy. If a rectal cancer's size or position make surgery difficult, radiation may be used before surgery to shrink the tumor. Radiation therapy can also be given to help control rectal cancers in people who are not healthy enough for surgery.

Radiation also may be used to ease (palliate) symptoms in people with advanced cancer causing intestinal blockage, bleeding, or pain.

Radiation treatment is often combined with chemotherapy. Chemotherapy helps make the radiation treatment more effective. Radiation therapy is more often used for rectal cancer but may also be used in some cases for colon cancer.

Radiation for Colon Cancer. Radiation for colon cancer is given after surgery (postoperative or adjuvant radiation) to destroy any remaining cancer cells. It is generally not used to treat metastatic colon cancer.

Radiation for Rectal Cancer. Adjuvant radiation is a common practice for patients with rectal cancer in Stages II and III. Radiation is used to help prevent cancer recurrence. In recent years, doctors have also begun administering chemotherapy and radiation before surgery for rectal cancer (neoadjuvant chemoradiation). The use of radiation before surgery can help shrink the size of the tumor. Pre-operative chemotherapy and radiation may also help preserve sphincter-muscle function and reduce the chance that a patient will need a colostomy.

Side Effects of Radiation Therapy

Side effects of radiation may include:

Diarrhea
Skin irritation around the anus
Incontinence
Bladder irritation
Fatigue
Sexual dysfunction in men and vaginal irritation in women

Resources

www.cancer.org -- American Cancer Society
www.cancer.gov -- National Cancer Institute
www.asco.org -- American Society of Clinical Oncology
www.cancer.net -- Cancer.Net
www.nccn.org -- National Comprehensive Cancer Network
www.fightcolorectalcancer.org -- Colorectal Cancer Coalition
www.cancer.gov/clinicaltrials -- Find clinical trials

References

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National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Rectal Cancer. V.3.2008.

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Reviewed last on: 12/1/2008
Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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