Prescribing trends of adjuvant neratinib in hormone-positive HER2 positive breast cancer.

BACKGROUND Neratinib is a potent tyrosine kinase inhibitor with activity against HER2-positive breast cancer (HER2+). The ExteNET study demonstrated a significant invasive disease-free survival benefit of neratinib in hormone receptor-positive (HR+) HER2+ breast cancer following trastuzumab-based adjuvant therapy. However, ExteNET was conducted before the use of pertuzumab or adjuvant trastuzumab emtansine (T-DM1). We evaluated clinical characteristics of patients prescribed neratinib in current practice.

METHODS We retrospectively reviewed patients with HR+ HER2+ breast cancer eligible for neratinib at our institution from 2017-2024. Clinical and treatment information was extracted from the electronic medical record. High-risk status was defined using traditional high-risk HR+ breast cancer features and literature supporting high Ki-67 and tumor grade as predictors of recurrence. Chi-square and t-tests were used for analysis.

RESULTS Among 107 eligible patients, 67 were offered neratinib and 40 were not. High-risk disease was significantly more prevalent in patients offered neratinib (p<0.01). Residual disease and progression rates did not differ significantly between groups.

CONCLUSION High-risk clinical features significantly influenced neratinib prescribing. Residual disease did not appear to impact prescribing decisions. These findings suggest biologic risk criteria may serve as practical guidelines for adjuvant neratinib use.