Immunotherapy of established micrometastases with Bacillus Calmette-Guérin tumor cell vaccine.

We evaluated the use of Bacillus Calmette-Guérin admixed with tumor cells as a vaccine to induce systemic tumor immunity for therapy of subclinical (micrometastatic) disease. In several experiments inbred strain 2 guinea pigs were given i.v. injections of either 10(4), 10(5), or 10(6) syngeneic L10 hepatocarcinoma cells, and initial vaccinations were administered either 1 or 4 days after tumor inocluation. Variables in vaccine preparation, such as ratio of viable Bacillus Calmette-Guérin organisms to tumor cells, procedures for freezing the tumor cells, X-ray treatment of tumor cells, and vaccination regimen were evaluated. The studies demonstrated that under defined conditions nontumorigenic vaccines of Bacillus Calmette-Guérin and tumor cells can cure the majority of animals of otherwise lethal visceral micrometastases.