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.