Discordance in receptor status between primary and recurrent breast cancer has a prognostic impact: a single Institution analysis

Background: Tumor phenotype may change during breast cancer progression. This study evaluates the prognostic impact of receptor discordance between paired primaries and recurrences.Patients and Methods: 139 patients underwent histological sampling of suspected breast cancer recurrence. All the pathology assessments (ER, PgR and HER2) on both primaries and confirmed recurrences were performed at the same laboratory. Results: A breast cancer recurrence was confirmed in 119 cases. Rates of discordance were 13.4%, 39% and 11.8% for ER, PgR and HER2, respectively. Ninety-two patients maintained the same tumor phenotype (i.e., the same hormone receptors and HER2 status) whereas 27 (22.7%) changed during progression. The loss of hormone receptor-positivity and the loss of HER2-positivity resulted in a worse post-recurrence survival (p=0.01 and p=0.008, respectively) and overall survival (p=0.06 and p=0.0002, respectively), compared to the corresponding concordant-positive cases. Tumor phenotype discordance was associated with worse post-recurrence and overall survival (p=0.006 and p=0.002, respectively); those cases who turned into triple-negative experienced the poorest outcome, respect to the concordant group (p=0.001, overall survival).Conclusions: We demonstrated for the first time an impact on overall survival of phenotype discordance between primary breast cancer and relapse. Among discordant cases, receptor-loss resulted the main determinant of poorer outcome