Rectal Cancer

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Radiation Therapy

Radiation therapy uses high-energy X-rays or other types of radiation to kill cancer cells.

People with rectal cancer often have radiation therapy before surgery (neoadjuvant radiation therapy) to shrink their tumor. This makes the tumor easier to remove from the small space in and around the rectum, and it decreases the chance that the cancer will return. If the cancer has spread (metastasized) to other parts of the body, radiation therapy may also be helpful for treating those specific spots.

Patients of Seattle Cancer Care Alliance (SCCA) may receive radiation therapy at these locations:

Intensity-Modulated Radiation Therapy (IMRT)

External-beam radiation therapy uses a machine called a linear accelerator to send beams of radiation toward the cancer. For rectal cancer, doctors most often use a type called intensity-modulated radiation therapy (IMRT). IMRT uses precise imaging and computers to map your tumor. This helps your radiation oncologist accurately plan your radiation therapy and target the beams to your tumor.

Radiation therapy treatments are given Monday through Friday for about five weeks. If your treatment involves radiation therapy, your radiation oncologist will determine the dosage and schedule for your treatments, will help you manage any side effects, and will work closely with other members of your care team. Learn more in the section on radiation oncology.

Chemotherapy and Radiation Together

If you’re having radiation therapy, you will most likely get chemotherapy at the same time. This combination is called chemoradiation. Chemotherapy drugs can make cancer cells more sensitive to radiation.

Intraoperative Radiation Therapy (IORT)

IORT is a fast and effective form of radiation therapy that uses electron-beam radiation during surgery. When tumors cannot be completely removed from the pelvic or abdominal regions because they are attached to important organs or nerves, or if cancer cells might have been left behind when a tumor was resected, surgeons can move normal structures out of the way during surgery to expose the area for this high-dose radiation treatment.

IORT takes only a few minutes to deliver and uses only a fraction of the total radiation given over a traditional multi-week course of external-beam treatment. It delivers precise radiation to the tumor while limiting exposure to surrounding tissues. UWMC is the only hospital in the Pacific Northwest to offer this treatment.

SCCA radiation oncologists use IORT to treat locally advanced rectal cancers that are attached to normal structures (such as nerves, blood vessels, or the pelvic side wall) that cannot be removed and to treat recurrent tumors. Learn more about IORT.

Side Effects of Radiation Therapy

Radiation therapy can cause side effects, which may depend on exactly how and where the radiation is given. Fatigue is a common side effect. Radiation therapy to the pelvic area may also cause gastrointestinal problems (like upset stomach and diarrhea), sexual problems, and infertility. Your team at SCCA will talk with you about the specific side effects you might experience, and we will help you prevent, reduce, or manage these effects as best as possible. You can find general information in the symptom management section.