Adjuvant therapy for carcinoma of the colon and rectum.

Because all types of cancer therapy are most effective when the tumor burden is small, adding adjuvant cancer treatment to surgical excision has great merit both in theory and experimentally. Even though large numbers of patients with large bowel cancer have been entered into various types of experimental trials over the past 25 years, the potential of multimodal cancer therapy has only been examined in a superficial manner at best. If this therapeutic approach had any substantial effectiveness, it would have long since become apparent. Surgical therapy is effective, with a five-year survival of 50%, and the various adjuvant therapies have shown only modest effectiveness when tested on patients with measurable disease. 5-Fluorouracil, with a response rate in measurable disease of approximately 20%, is the only consistently effective cancericidal drug, and its combination with other agents has thus far shown no increase in this response rate. Currently, available data would indicate a modest survival benefit from the use of postoperative 5-fluorouracil, particularly in patients with positive lymph nodes. There are a number of trials in progress studying the effectiveness of multiple drug combinations as well as combining chemotherapy with radiotherapy and/or immunotherapy in the adjuvant setting. Preliminary studies would suggest a benefit from infusing chemotherapy into the liver in the immediate postoperative period, although there has been no evidence substantiating improved survival from this approach. The multiple approaches for generating an effective immunologic response continue to be experimental and have little use in other than a highly controlled experimental environment. The use of radiotherapy as an adjuvant to surgery has been confined largely to patients with low-lying rectal cancer. There is substantial evidence that high-dosage radiotherapy for large bulky and fixed rectal cancer will result in shrinkage of the lesion, permitting more satisfactory surgical resection and decreasing the incidence of perineal recurrence. Evidence would also suggest that moderate-dosage preoperative radiotherapy may sufficiently alter cancer cells so that cells disseminated at the time of operation are no longer capable of growth. It has also been demonstrated that preoperative radiotherapy decreases the incidence of positive lymph nodes. Modest increase in survival following preoperative radiotherapy has also been demonstrated in numerous trials. Postoperative radiotherapy has not been tested for a sufficient period of time to either demonstrate its effectiveness or safety.(ABSTRACT TRUNCATED AT 400 WORDS)