The impact of ERBB-family germline single nucleotide polymorphisms on survival response to adjuvant trastuzumab treatment in HER2-positive breast cancer

Background: Trastuzumab treatment for women with HER2-positive breast cancer (BC) resulted in the significant improvement of both relapse free survival (RFS) and overall survival (OS). However, many women who are classified as HER2-positive do not respond. Many studies have focused on the role of somatic mutations rather than germline polymorphisms in trastuzumab resistance.

Results: We completed an Agena MassArray screen of 10 ERBB-family single nucleotide polymorphisms (SNPs) in 194 adjuvant trastuzumab treated HER2-positive BC patients. SNPs in EGFR genes have a significant association with RFS and OS. Patients with the minor allele of EGFR N158N had significantly worse OS (hazard ratio (HR) = 4.01, (confidence interval (CI) = 1.53- 10.69), p = 0.05) relative to those with either the heterozygous or wild-type (WT) allele. Patients with the minor allele of EGFR T903T (HR = 3.52, (CI = 1.38- 8.97), p = 0.05) had worse RFS relative to those with either the heterozygous or WT allele.

Patients and methods: Using next generation sequencing (NGS) we identified ERBB-family (EGFR, HER2, HER3 and HER4) single nucleotide polymorphisms (SNPs) that occurred in 2 or more patients of a 32 HER2-positive BC patient cohort. Agena MassArray analysis confirmed the frequency of these SNPs in 194 women with HER2-positive BC who received trastuzumab in the adjuvant setting. Using Kaplan-Meier estimates and Cox regression analysis we correlated the presence of ERBB-family SNPs with both RFS and OS.

Conclusions: The presence of germline ERBB-family SNPs may play an important role in how a patient responds to adjuvant trastuzumab, and clinical assessment of these SNPs by targeted genetic screening of patients' blood may be important to stratify patients for treatment.