THE ANTIMETASTATIC EFFECT OF IV-INOCULATED BCG ON ADENOCARCINOMAS IN THE PROSTATE-SEMINAL VESICLE COMPLEX OF L-W RATS

Adenocarcinomas were induced in the prostate-seminal vesicle complex o f Lobund-Wister (L-W) rats by a single IV inoculation of N-methyl-N-ni trosourea. This was followed by three slow-release S.C. implants of te stosterone propionate, each at intervals of 2 months. Small (0.5 cm di ameter) palpable tumors developed which enlarged during the following month to 3.4 cm diameter. At the latter stage, tumor cells spread via lymphatics to the lungs and/or by direct extension into the peritoneal cavity. Rats with small palpable tumors were inoculated IV with viabl e Bacillus Calmette-Guerin (BCG). One month later, the rats were kille d and examined. Untreated rats with large tumors served as controls. C omparison of the two groups revealed that body weights and tumor sizes were similar and most of them had developed metastatic tumors in the peritoneal activity. However, lung metastases were rare in the BCG-ino culated rats compared to controls. Spleen and liver weights were signi ficantly heavier in the BCG-treated rats. It is speculated that an int ra-vascular mechanism(s), engendered by BCG, immobilized the circulati ng tumor cells, but not those tumor cells that spread by direct extens ion from the primary tumor into the peritoneal cavity.