Interaction of the progesterone receptor expression with other prognostic factors in primary breast cancer.

e11119 Background: The expression of the estrogen receptor (ER) and the progesterone receptor (PR) is a predictive factor for the response to an endocrine treatment and to chemotherapy in primary breast cancer. Aim of this retrospective study was to analyse the prognostic relevance of PR in interaction with other prognostic factors. Methods: Between 1995 and 2008, data from 5144 patients with primary breast cancer have been collected in 3 German university hospitals. The PR-expression was correlated to clinical-pathological variables like tumor stage, nodal status, grading and the expression of ER. Overall survival (OS), distant disease free survival (DDFS) and local recurrence free survival (LRFS) were the main outcomes of interest. PR was analysed for interaction with each other prognostic factor in cox proportional hazard models. Results: The expression of the progesterone receptor had an effect on overall and distant disease free survival (each < 0,001), but no effect on local recurrence free survival (p = 0,382). The only interaction of the PR status and other prognostic factors was seen for the ER status (p = 0,028). Women with ER negative/PR negative tumors had an worse prognosis than patients with ER negative/PR positive tumors. Women with ER negative/PR positive tumors had an equal prognosis than patients with ER positive/PR positive disease. There is no interaction between the PR status and the tumor stage, nodal status and grading. Conclusions: Expression of PR is an independent prognostic factor. In addition to ER, PR should be analysed to identify subgroups with different clinical outcome.