RECTAL CANCER AND OTHER GASTROINTESTINAL CANCERS
Anal Cancer
Squamous cell carcinoma of the anal canal has been treated in the past by an operation to remove the anus and rectum, requiring a permanent colostomy. In recent years, this operation has been supplanted by radiation therapy. The odds of cure are essentially the same for either surgery or radiation therapy, and radiation therapy has the advantage of preserving the anus and rectum, thus avoiding a colostomy.
Before any treatment is started, the recommended treatment, the reasons it is recommended, the procedures to be carried out, the expected or possible side effects or complications, and the expected benefits are all explained to the patient and family. The patient must give permission for treatment, based on this knowledge ("informed consent"), before treatment is given.
Radiation is given once daily, 5 days a week, for approximately 6 to 6½ weeks. The treatment is usually combined with chemotherapy for patients who have more advanced cancers. The chemotherapy is usually either fluorouracil (5-FU) combined with either mitomycin C or cisplatin. The chance of cure with a combination of chemotherapy and radiation therapy is approximately 75% to 80%. Cure rates are higher for earlier stage, T1 and T2 cancers and somewhat lower for patients with more advanced disease.
Squamous cell carcinoma of the anal margin (that is, the perianal skin) may be treated either with a local excision or limited-field irradiation if the tumor is small (stage T1) and the cancer cells are well to moderately differentiated. Because larger cancers, 2 to 4 cm in maximum diameter, have an increased risk of spread to the inguinal lymph nodes, both the primary cancer and the inguinal nodes are treated with irradiation. Patients with more advanced cancers (stages T3 or T4) or with lymph nodes known to contain cancer are treated with irradiation and chemotherapy, employing the same techniques used for patients with anal canal cancers.
