Even with the best surgical technique, it is difficult to remove all cancer cells from the tissue surrounding a rectal cancer tumor. In order to destroy any remaining cancer cells, radiation therapy is often used either before or after surgery to reduce the risk that cancer will return in the locally in the rectum.
Chemotherapy makes cancerous tissues more sensitive to radiation, which allows the radiation to destroy more cancer cells. The combination of radiation and chemotherapy is called chemoradiation, and is generally given in two ways:
- Neoadjuvant chemoradiation: Given before surgery, chemoradiation can reduce the size of tumors, the risk that they will recur locally, and the need for permanent colostomy. It is now the recommended treatment for stage II and III rectal cancer, if the cancer has been clinically staged.
- Adjuvant chemoradiation: Given after surgery, chemoradiation can reduce the risk that cancer will return in the rectum. It is recommended for rectal cancers initially clinically staged as stage I (T1 or T2) that are found by the pathologist after surgery to go into through wall of the rectum (T3) or have spread to nearby lymph nodes.
- Continuous infusion 5-FU and external beam radiation (EBRT). Treatment usually lasts several weeks. With continuous infusion 5-FU, the chemotherapy drug is delivered intravenously through a pump carried in a fanny pack.
- Bolus 5-FU and external beam radiation. Less often recommended.
- Oral Xeloda® (capecitabine) and radiation.
- A clinical trial that adds Eloxatin® (oxaliplatin) or Eloxatin plus Avastin® (bevacizumab) to Xeloda.
Side effects from radiation therapy
Although treatments are carefully planned to focus radiation on the tumor and the immediately surrounding rectum and mesentery, it is almost impossible to avoid damaging healthy tissue. Side effects from treatment include:
- Redness and skin irritation. Ask your radiation oncologist for creams to soothe burns.
- Irritation of rectal tissues that can cause diarrhea, rectal bleeding, painful bowel movements, or bowel incontinence.
- Bladder irritation causing frequent urination, blood in the urine, or burning during urination.
- Sexual problems: impotence in men and vaginal irritation in women that may make intercourse painful.
Where Can You Go for More Information
NCI Radiation Therapy and You is available online and answers many questions about radiation treatments, side effects, and how to manage them/
RT Answers, a website sponsored by the American Society for Therapeutic Radiology and Oncology (ASTRO) explains more about radiation treatment for rectal cancer.