Among patients with human epidermal growth factor receptor 2–positive (HER2+) breast cancer, adding trastuzumab to adjuvant chemotherapy reduces risk of recurrence for at least 10 years, according to investigators.
The benefit of trastuzumab was greater among patients with hormone receptor–positive (HR+) disease than those with HR– disease until the 5-year timepoint, after which HR status had no significant impact on recurrence rates, reported lead author, of the Mayo Clinic in Jacksonville, Fla., and colleagues. This finding echoes a pattern similar to that of HER2– breast cancer, in which patients with HR+ disease have relatively consistent risk of recurrence over time, whereas patients with HR– disease have an early risk of recurrence that decreases after 5 years.
“To the best of our knowledge, this analysis is the first to address the risk of late relapses in subsets of HER2+ breast cancer patients who were treated with adjuvant trastuzumab,” the investigators wrote. Their report is in.
They drew data from 3,177 patients with HER2+ breast cancer who were involved in two phase 3 studies: the North Central Cancer Treatment Group N9831 and National Surgical Adjuvant Breast and Bowel Project B-31 trials. Patients involved in the analysis received either standard adjuvant chemotherapy with cyclophosphamide and doxorubicin followed by weekly paclitaxel or the same chemotherapy regimen plus concurrent trastuzumab. The primary outcome was recurrence-free survival, which was defined as time from randomization until local, regional, or distant recurrence of breast cancer or breast cancer–related death. Kaplan-Meier estimates were performed to determine recurrence-free survival, while Cox proportional hazards regression models were used to determine factors that predicted relapse.
Including a median follow-up of 8 years across all patients, the analysis showed that those with HR+ breast cancer had a significantly higher estimated rate of recurrence-free survival than that of those with HR– disease after 5 years (81.49% vs. 74.65%) and 10 years (73.84% vs. 69.22%). Overall, a comparable level of benefit was derived from adding trastuzumab regardless of HR status (interaction P = .87). However, during the first 5 years, HR positivity predicted greater benefit from adding trastuzumab, as patients with HR+ disease had a 40% lower risk of relapse than that of those with HR– disease (hazard ratio, 0.60; P less than .001). Between years 5 and 10, the statistical significance of HR status faded (P = .12), suggesting that HR status is not a predictor of long-term recurrence.
“Given concerning adverse effects and potentially smaller benefit of extended adjuvant endocrine therapy, particularly in patients with N0 or N1 disease, our findings highlight the need to develop better risk prediction models and biomarkers to identify which patients have sufficient risk for late relapse to warrant the use of extended endocrine therapy in HER2+ breast cancer,” the investigators concluded.
The study was funded by the National Institutes of Health, the Breast Cancer Research Foundation, Bankhead-Coley Research Program, the DONNA Foundation, and Genentech. Dr. Chumsri disclosed a financial relationship with Merck. Coauthors disclosed ties with Merck, Novartis, Genentech, and NanoString Technologies.
SOURCE: Chumsri et al. J Clin Oncol. 2019 Oct 17.