[Adjuvant and palliative immunotherapy of colorectal carcinoma]

A review of the clinical trials on immune therapies in cancer reveals that this approach can, in rare cases, induce complete remissions in individual cancers. Since these trials have usually involved patients with large tumor masses, tumor cell inaccessibility is probably a major reason for the prevailing failures. Minimal residual disease, the stage when tumor cells are few and dispersed, should therefore be a more promising target for immunological approaches. This hypothesis is supported by a prospective randomized trial on patients with resected Dukes C colorectal carcinoma. 189 patients were assigned to an observation regimen or to postoperative treatment with 500 mg of 17-1A antibody, followed by four 100 mg infusions each month. After a median follow-up of five years, antibody treatment reduced the overall death rate by 30% and decreased the recurrence rate by 27%. The effect of antibody was most pronounced in patients who had distant metastasis as first sign of a relapse, an effect that was not seen for local relapses. Thus in addition to strategies designed to produce more effective reagents, efforts need to be concentrated on directing immunological effectors towards the appropriate target.