Prognostic significance of single progesterone receptor positivity a comparison study of estrogen receptor negative/progesterone receptor positive/her2 negative primary breast cancer with triple negative breast cancer

Single progesterone receptor positive (PgR), especially in form of ER/PgR/HER2, is a nonnegligible phenomenon. Little is known about the characteristics and the role of single PgR positive in this phenotype. Therefore, we explore the significance of single PgR positivity by comparing ER/PgR/HER2 breast cancers with triple negative breast cancers (TNBCs). Three thousand nine hundred sixty-six cases of primary invasive breast carcinoma operated consecutively from January 2005 to May 2008 in Cancer Hospital, Chinese Academy of Medical Sciences were examined. Two hundred forty (6%) cases were identified as ER/PgR/HER2 breast cancers and 348 (8.8%) cases as TNBCs. Clinicopathological characteristics and survivals were analyzed respectively and then compared between 2 subtypes. Compared with patients with TNBCs, ER/PgR/HER2 tumor tended to have lower tumor grade (Grade 3: 45.7% vs. 37.5%, P0.051) and smaller tumor size (P0.036). However, no differences were found between ER/PgR/HER2 and TNBC patients in relapse-free survival (RFS) and OS. The 5-year RFS rates were 80.7% and 77.4%, respectively (P0.330) and the 5-year OS rates were 88.0% and 85.2%, respectively (P0.290). ER/PgR/HER2 patients receiving adjuvant endocrine treatment had better RFS (P0.016) and overall survival (OS) (P<0.0001) than patients receiving no endocrine therapy. This exclusive analysis of patients with ER/PgR/HER2 breast cancers showed that this subtype exhibited an aggressive behavior as TNBC, suggesting that it should also be regarded as biologically distinctive group and single PgR positive itself is not a good prognostic factor. However, adjuvant endocrine therapy could still benefit this group of patients. Further investigations should be done to elucidate the underlying mechanism.