Purpose: Neoadjuvant chemotherapy (NCT) plus anti-HER2 agents are the standard of care for locally advanced HER2-positive breast cancer. The aim of this study was to evaluate the prevalence and prognostic impact of HER2 loss in patients with HER2-positive disease treated with neoadjuvant therapy with or without trastuzumab.
Methods: 549 consecutive HER2-positive patients were included in this study. 379 patients were treated with paclitaxel, carboplatin, and trastuzumab (PCH cohort) and 170 were treated with paclitaxel and carboplatin only (PC cohort). Conversion of biomarkers before and after NCT was evaluated via immunohistochemistry (IHC) test. Cox regression model was used to investigate prognostic markers to relapse-free survival (RFS).
Results: 50.9% patients were considered as pCR responder in PCH cohort, whereas only 25.9% of patients experienced pCR in PC cohort (P < 0.001). HER2 loss were more frequently shown in PCH cohort with a proportion of 19.8%, compared to 9.4% in PC cohort (P = 0.009). In PCH cohort, patients with a loss of HER2 expression tended to have a higher risk of relapse compared to patients with maintained HER2 expression (HR = 2.639, 95% CI 1.103-6.311, P = 0.029). However, it did not correlate to patient outcome in the PC cohort (P = 0.296). Loss of HER2 was also correlated to ER conversion in PCH cohort.
Conclusion: Our study has provided new evidence that anti-HER2 treatment has a significant impact on HER2 loss. Far more importantly, the loss of HER2 amplification could identify non-pCR patients with high risk of disease relapse, which might help in tailoring following systemic treatment.
Keywords: Breast cancer; HER2-positive; Neoadjuvant chemotherapy; Pathological complete response; Trastuzumab.