Prognostic Factors in an Exercised Model of Chemically-induced Mammary Cancer.

Background/aim: Estrogen receptor α (ERα) and Ki-67 are strong prognostic and predictive markers in woman breast cancer. This study aimed to evaluate the immunoexpression of prognostic factor markers ERα, Ki-67 proliferation index (Ki-67 PI) and the mitotic activity index (MAI) in mammary tumors induced by 1-methyl-1-nitrosourea (MNU) in female Sprague-Dawley rats submitted to lifelong exercise training.

Materials And Methods: Thirty female rats were injected with MNU and randomly divided into two groups: sedentary and exercised.

Results: All neoplasms from both groups were ERα-positive with an H-score ≥20. Statistically significant differences were not found in the ERα H-score, Ki-67 PI and MAI between groups. The absolute value of ERα H-score was higher in the exercised group, while the Ki-67 PI and MAI were higher in the sedentary group.

Conclusion: Tumors from the exercised group were less proliferative and more differentiated, suggesting that long-term exercise training had positive effects on mammary carcinogenesis.