Efficacy of neoadjuvant treatment with or without pertuzumab in patients with stage II and III HER2-positive breast cancer: a nationwide cohort analysis of pathologic response and 5-year survival

Background: Pathologic complete response (pCR) rates in early stage HER2-positive breast cancer improved after pertuzumab was added to neoadjuvant treatment. However, survival benefit is less-well established and seems mostly limited to node-positive patients. We used national cancer registry data to compare outcomes of patients treated with and without pertuzumab. Methods: We identified stage II-III HER2-positive breast cancer patients treated with neoadjuvant trastuzumab-based chemotherapy between November 2013 until January 2016 from the Netherlands Cancer Registry. Dur-ing that period pertuzumab was only available in the 37 hospitals that participated in the TRAIN-2 study. Missing grade and pCR-status were obtained from the Dutch Pathology Registry (PALGA) and cause of death from Sta-tistics Netherlands. We used multiple imputation to impute missing data, multivariable logistic regression to evaluate the association between pertuzumab and pCR (ypT0/is, ypN0) and multivariable Cox regression models for overall survival and breast cancer specific survival (BCSS). Results: We identified 1124 patients of whom 453 received pertuzumab. Baseline characteristics were compa-rable, although tumor grade was missing more often in patients treated without pertuzumab (12% vs. 2%). Pertuzumab improved pCR rates (41% vs 65%, adjusted odds ratio [aOR] 2.91; 95% CI:2.20-3.94). After a median follow-up of 6.0 years, 5-year BCSS rates were 95% and 98% respectively (adjusted hazard ratio [aHR]: 0.58; 95% CI:0.36-0.95). Younger patients derived more benefit from pertuzumab, but no other significant in-teractions were found. Conclusion: These results support earlier data of a small survival benefit with the addition of pertuzumab to trastuzumab-based neoadjuvant chemotherapy which is most meaningful in younger patients.

Automated summary

This study compared the outcomes of early stage HER2-positive breast cancer patients treated with and without pertuzumab using national cancer registry data. The results showed that pertuzumab improved pCR rates and provided a small survival benefit, which was most significant in younger patients.