Effects of methanol extraction residue and therapeutic irradiation against established isografts and simulated local recurrence of mammary carcinomas.

Female BALB/c mice carrying established isografts or simulated local recurrence implants of 2 rapidly growing mammary adenocarcinomas were treated either by injection of the methanol extraction residue (MER) fraction of killed Bacillus Calmette-Guérin organisms (given s.c. or into the tumor) or by focal X-irradiation or by both. None of the modalities of therapy effected cures, but in many instances there was a significant retardation of tumor cevelopment and prolongation of the lives of the mice. Administration of MER alone offered protection in a number of cases but less often than the other forms of treatment. Combined therapy with MER and irradiation was, on the whole, the most successful therapeutic intervention. MER or irradiation administered alone enhanced the neoplastic process only on rare occasions; this appeared to be the case even more infrequently with combined treatment. MER was most likely to be effective alone or in combination when small quantities were used and when only 1 treatment or 1 cycle of combined therapy was given. The therapeutic action of MER was not dependent on direct introduction of the agent into a neoplastic focus; s.c. administration distal to the tumor site was almost always at least as satisfactory as injection directly into the tumor mass and indeed was often more efficacious.