Meta-analysis of the impact of progesterone receptor status on oncological outcomes in oestrogen receptor-positive breast cancer

Background: Assessment of the oestrogen receptor (ER) provides important prognostic information in breast cancer. The impact of progesterone receptor (PgR) status is less clear. Standardization of immunohistochemical analysis of these receptors has reduced interstudy heterogeneity. The aim of this meta-analysis was to evaluate the impact of PgR negativity on outcomes in ER-positive (ER+) breast cancer. Methods: This study was performed according to PRISMA and MOOSE guidelines. PubMed, Embase and the Cochrane Library were searched systematically to identify studies comparing disease-free survival as the primary outcome and overall survival as secondary outcome between PgR-positive (PgR+) and PgR-negative (PgR–) status in ER+ breast cancer. A meta-analysis of time-to-effect measures from included studies was undertaken. Results: Eight studies including 13 667 patients, 11 838 in the ER+PgR+ group and 1829 in the ER+PgR– group, met the inclusion criteria. Treatment characteristics did not differ significantly between the two groups. Patients in the ER+PgR– group had a higher risk of disease recurrence than those who had ER+PgR+ disease (hazard ratio (HR) 1·57, 95 per cent c.i. 1·38 to 1·79; P < 0·001). This hazard was increased in patients with human epidermal growth factor receptor 2-negative tumours (HR 1·62, 1·37 to 1·93; P < 0·001). A similar result was observed for overall survival (HR 1·69, 1·33 to 2·14; P < 0·001). Conclusion: PgR negativity is associated with significant reductions in disease-free and overall survival in ER+ breast cancer. Treatment and surveillance strategies in these patients should be tailored accordingly.