Biologic and clinical characteristics of breast cancer with single hormone receptor positive phenotype.

PURPOSE: Response to endocrine therapy in breast cancer correlates with estrogen receptor (ER) and progesterone receptor (PgR) status. It is usually easier to decide treatment strategies in cases of double-positive/-negative phenotypes than in single-positive tumors.

PATIENTS AND METHODS: We have examined a large and well-characterized series of primary invasive breast carcinoma (1,944 cases) with long-term clinical follow-up and hormone therapy data. Patients were stratified according to ER and PgR expression and the study was focused on the single-positive groups (ER-/PgR+ and ER+/PgR-), to assess their main features and evaluate any prognostic and predictive difference between them and compare them with the double-positive/-negative tumors.

RESULTS: ER+/PgR-tumors were found more frequently in elderly, postmenopausal women. The majority were grade 2 ductal/no specific type carcinomas. There was no difference between the two groups with regard to lymph node stage. Survival analyses showed no difference between the two groups in terms of disease-free interval and overall survival. However, when compared with the double-negative phenotype, ER+/PgR-showed an association with better outcome but no such survival advantage was detected in case of ER-/PgR+ tumors. In the group of patients with ER+ tumors who received adjuvant hormonal therapy, absence of PgR (ER+/PgR-) was an independent predictor of development of recurrence and shorter survival and, hence, poorer response to hormonal therapy.

CONCLUSION: ER+/PgR-and ER-/PgR+ tumors are biologically and clinically distinct groups of breast cancer that may require different treatment strategies with ER-/PgR+ exhibiting more aggressive behavioral characteristics.