Dr Waks on Survival Outcomes With Chemotherapy in Small Node-Negative HER2+ Breast Cancer

Adrienne G. Waks, MD, physician, associate director of Clinical Research, Dana-Farber Cancer Institute, instructor in medicine, Harvard Medical School, discusses breast cancer survival in patients with small node-negative HER2-positive breast cancer according to the treatment modality received.

An analysis of treatment patterns and patient outcomes was conducted to clarify the benefit of systemic therapy for the treatment of patients with small, node-negative HER2-positive breast cancer across stage I tumor size.

Patients with a single lifetime diagnosis of pT1N0 HER2+ breast cancer between 2010 and 2019 were identified utilizing the national Surveillance, Epidemiology and End Results (SEER) database. Their prior exposure to chemotherapy was categorized as yes, no, or unknown. All systemic therapy was administered in the adjuvant setting. The primary objective was breast cancer-specific survival. Notably, SEER did not contain data on prior endocrine therapy or recurrence events. Within each tumor stage, patients were categorized as hormone receptor (HR)–positive (n = 9513) or HR-negative (n = 3348).

Results showed that patients with stage IA and IB tumors of 1cm or less had high rates of 5-year breast cancer-specific survival with or without chemotherapy, Waks reports. Patients with pT1a HR-positive HER2-negative disease had rates of 99.8% with chemotherapy. In the pT1B HR-positive group, this rate was 99.3%. In the HR-negative group, patients with pT1A tumors had a survival rate of 98.4% with chemotherapy, and those with pT1B tumors had a rate of 98.9%.

Moreover, patients with HR-positive pT1C tumors between 1 cm and 2 cm had survival rates of 98.7% with chemotherapy, Waks continues. Patients in this group with HR-negative tumors had a rate of 96.7%.

Larger tumors did have an increase in events, indicating that chemotherapy administration for these patients was correlated with tumor size, Waks notes. Overall, chemotherapy administration was associated with a higher breast cancer-specific survival rate in the stage IA cohort, and more specifically in patients with HR-positive, HER2-negative stage 1A tumors.

Disclosures: Dr. Waks reports serving as a consultant or in an advisory role for AstraZeneca; she received research funding from Genentech, MacroGenics and Merck.