Enhancement of metastasis development by BCG immunotherapy

When BALB/c mice bearing growing transplants of a syngeneic colon carcinoma--Colon Tumor 26 (CT 26)--were treated with Bacillus Calmette-Guerin (BCG), no effect on tumor growth rate or survival time was observed compared to untreated controls. However, after excision of primary tumor transplants, enhanced development of lung metastases was noted in the BCG-treated mice, resulting in both as increased mortality rate (from metastatic disease) and a shorter survival time.