Evaluation of intratumoral immunostimulants in the treatment of a transplantable rat mammary carcinoma

Abstract

One C. parvum preparation and two BCG (Bacillus Calmette-Guérin) strains have been evaluated for their effects, when injected intratumorally, on established growths of a transplantable rat mammary carcinoma of spontaneous origin. It was found that whilst the anti-tumor effect of intratumoral injection varied from experiment to experiment certain conclusions could be drawn. Thus for maximal effect the injection should be given as early as possible and at a high dose; furthermore, multiple intratumoral injections appeared to offer no advantage over a single injection. It was also apparent that the anti-tumor effect following intratumoral injection of C. parvum or BCG was not improved when the tumor-bearing animals were presensitised to these immunostimulants. Intratumoral C. parvum was also used as an adjunct to surgery in the treatment of metastases; however, in this model it did not improve the effect of surgery alone. It is concluded that under certain defined circumstances intratumoral injection can bring about tumor regression. However, the conditions under which it is effective may render this form of treatment of limited application.