Long survival of patients with small cell lung cancer after adjuvant treatment with the anti-idiotypic antibody BEC2 plus Bacillus Calmette-Guérin.

Despite active therapies for small cell lung cancer (SCLC), most patients relapse and die of the disease. The present study evaluates immunization using the anti-idiotypic antibody BEC2, which mimics the ganglioside GD3 expressed on the surface of most SCLC tumors, combined with Bacillus Calmette-Guérin (BCG) as an immune adjuvant. We hypothesized that active immunization could alter the natural history of the disease. Fifteen patients who had completed standard therapy for SCLC received a series of five intradermal immunizations consisting of 2.5 mg of BEC2 plus BCG over a 10-week period. Blood was collected for serological analysis, and outcome was monitored. All patients developed anti-BEC2 antibodies, despite having received chemotherapy with or without thoracic radiation. We detected anti-GD3 antibodies in five patients, including those with the longest relapse-free survival. The median relapse-free survival for patients with extensive stage disease is 11 months and has not been reached for patients with limited stage disease (>47 months), with only one of seven patients having relapsed after a median follow-up of 47 months. Immunization of patients with SCLC after standard therapy using BEC2 plus BCG can induce anti-GD3 antibodies and is safe. The survival and relapse-free survival in this group of patients are substantially better than those observed in a prior group of similar patients. A Phase III trial is being conducted to evaluate BEC2 plus BCG as adjuvant therapy after chemotherapy and irradiation.