Prognostic role of progesterone receptor expression in a population-based analysis.

PURPOSE: The role of progesterone (PR) expression in the management of breast cancer is controversial. The aim of this study is to evaluate the characteristics and prognosis of progesterone status among breast cancers patients in a population-based analysis.

MATERIALS AND METHODS: Through the Tuscan Cancer Registry data on all the invasive breast cancer cases diagnosed during the period 2004-2005 in the provinces of Florence and Prato, central Italy, were retrieved. Histological reports were re-examined to obtain information on the percentage of positive tumor cells for estrogen (ER), progesterone (PR) receptors, Ki67 marker and human epidermal growth factor 2 (HER2). Information on age, stage, differentiation grade were also obtained.

RESULTS: Out of 1487 patients, 28% had PR- breast cancer. These patients were older (p 0.006) than PR+ cancer patients, with more frequently high Ki67 (p < 0.0001), HER2 + (p < 0.0001), ER- (p < 0.0001) tumoral expression. The ER+/PR+ subtype was the most represented (n.1053), while ER-/PR+ was the most rare (n.23); 210 cases (14.1%) ER+ PR- and 201 (13.5%) ER-/PR- cases were found. Analysis of survival by the Cox proportional hazards model showed an independent prognostic value of PR expression (p < 0.0001), also when estrogen, Ki67, HER2 status and age were included. The 5-year cancer-specific survival was 82.1, 86.5, 100, 92% for ER-/PR-, ER+/PR-, ER-/PR+, ER+/PR+ subtype, respectively.

CONCLUSIONS: Our study revealed significant differences in clinicopathological characteristics among breast cancer according to PR expression and confirmed its prognostic independent role, suggesting a role of PR in the improvement of breast cancer prognostic characterization.