Surgical adjuvant immunotherapy for colorectal cancer.

One hundred forty-four Wistar-Furth rats in 12 therapeutic groups have been studied in a long-term comparison of the effectiveness of nonspecific immunotherapy with MER (methanol extraction residue) vs active-specific immunotherapy with neuraminidase-modified tumor cells. Six months after surgical adjuvant immunotherapy a 100% improvement in survival was achieved with MER immunotherapy compared to untreated control animals. In addition, the use of MER enhanced the value of active-specific immunotherapy where both modalities were combined in sequence. The predicted value of MER-BCG (Bacillus Calmette-Guerin) for the immunotherapy of solid tumors was borne out by these results suggesting that present ongoing clinical trials of MER as adjuvant therapy for large bowel cancer should prove to be successful if properly controlled. The pattern of survival in these experiments suggests that surgical adjuvant immunotherapy is cytostatic rather than cytocidal, and implies the need for long-term, repeated immunizations.