Postoperative active-specific immunotherapy of lymph node micrometastasis in a guinea pig tumor model.

Strain 2 guinea pigs bearing the transplanted intradermally growing line 10 tumor underwent surgical tumor excision at a time when the tumor had already metastasized to the first draining lymph node. Postoperative active-specific immunotherapy (ASI) consisted of two vaccinations with either Newcastle disease virus (NDV) modified or BCG-admixed line 10 tumor cells. 32% of the animals were cured of residual lymphatic micrometastasis by ASI with NDV-modified tumor cells while ASI with BCG was successful in 45%. No synergistic effect was observed when both ASI procedures were combined. Vaccine preparations with mitomycin C inactivated tumor cells proved to be less (NDV) or noneffective (BCG) compared to those with irradiated tumor cells.