Role of adjuvant therapy in colorectal cancer

After nearly three decades of consistently disappointing adjuvant therapy trials in resectable colorectal cancer, recently emerging results offer some basis for cautious optimism. Adjuvant fluorouracil-containing regimens appear to confer a modest treatment benefit in completely resected colonic adenocarcinomas. The two most promising chemotherapy approaches at present appear to be the fluorouracil-levamisole and fluorouracil-leucovorin regimens. The optimal schedule and dose of these agents remains to be determined. Portal vein chemotherapy infusion studies have yielded promising but inconclusive results to date. As data from completed or ongoing large group studies become available, the role of this modality will be better clarified. In rectal cancer, adjuvant radiotherapy alone has a modest but consistent ability to reduce local recurrence without demonstrating any survival advantage. The optimal dose and sequencing of radiotherapy remains poorly defined. Two completed cooperative group studies strongly suggest that the optimal use of radiotherapy is in combination with chemotherapy. The independent role of chemotherapy in rectal cancer remains unclear. There is suggestive evidence that adjuvant chemotherapy is more effective with rectal cancer than with primaries arising proximal to the peritoneal reflection. Despite the large number of unresolved questions that remain, the following interim treatment recommendations can be made: 1. Patients with Dukes' B and C rectal and colonic adenocarcinomas should be entered into an appropriate adjuvant clinical trial when feasible. 2. Outside the setting of a protocol, there is a sound rationale to treat Dukes' B and C rectal cancer with combination chemotherapy and postoperative radiotherapy. The chemotherapy could consist of fluorouracil either alone or combined with leucovorin. 3. In more proximal colonic tumors (above the pelvic peritoneal reflection), recently described improvements in survival for patients with Dukes' B disease suggests that adjuvant therapy should be withheld in this group when not participating in a clinical study. Patients with Dukes' C tumors should receive fluorouracil-levamisole.