Effects of thymectomy on mammary tumor growth

The effect of thymectomy on prognosis following mammary tumor excision was evaluated in female C 3H MTV + mice, 5 to 6 months old, with spontaneous tumors 0.5 to 1 cm in diameter after random allocation to thymectomy or sham operation. Significant differences between these two groups were noted in absolute survival, disease-free survival, interval to tumor reappearance, and survival following tumor reappearance. Thymectomy prolonged survival both in tumor-free and tumor-bearing mice and delayed the reappearance of the tumors. The results indicate that thymectomy, when used as an adjuvant to surgical ablation of mammary tumors, has a therapeutic role. Both the previously reported protective effect of thymectomy against the risk of mammary neoplasia and the observed protective role following tumor occurrence could be attributed to its metabolic and immunoregulatory effects.