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: One hundred and thirty-nine patients underwent histological sampling of suspected breast cancer recurrence. All the pathology assessments [ER, PgR and human epidermal growth factor receptor 2 (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 (HR) and HER2 status], whereas 27 (22.7%) changed during progression. The loss of HR 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 (OS; P=0.06 and P=0.0002, respectively), compared with the corresponding concordant-positive cases. Tumor phenotype discordance was associated with worse post-recurrence and OS (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, OS).
Conclusions: We demonstrated for the first time an impact on OS of phenotype discordance between primary breast cancer and relapse. Among discordant cases, receptor loss resulted in the main determinant of poorer outcome.