CHICAGO – Treatment with paclitaxel and trastuzumab continued to demonstrate a low risk for recurrence when used as adjuvant therapy for breast cancer, according to a 7-year follow-up analysis from the APT trial presented at the ASCO Annual Meeting.
“Retrospective data suggest that patients with small, HER-2–positive cancers have more than just minimal risk of disease recurrence,” the researchers wrote. “The APT trial was designed to address treatment for such patients.”
Sara M. Tolaney, MD, MPH, senior physician and associate director of clinical research, breast oncology, at the Susan F. Smith Center for Women's Cancers and assistant professor of medicine at Harvard Medical School, and colleagues enrolled patients with HER-2–positive breast cancer (IHC 3+ and/or FISH ratio > 2.0) in this single-arm, multicenter, phase 2 study. Patients were required to have a tumor less than three centimeters in size and negative nodes, although one axillary lymph node micro-metastasis was permitted.
The primary endpoint was DFS. Recurrence-free interval, breast cancer-specific survival and OS were also evaluated.
Tolaney and colleagues enrolled 410 patients during the 3-year recruitment period; 406 started on treatment. Many patients (67%) had hormone receptor–positive tumors, but distribution by tumor size varied: less than or equal to 1 mm in greatest dimension (2%), greater than 1 mm but less than or equal to 5 mm (17%), greater than 5 mm but less than or equal to 10 mm (30%), greater than 10 mm but less than or equal to 20 mm (42%) and tumor less than or equal to 3 cm (9%). Six patients had a nodal micro-metastasis.
During a median follow-up of 6.5 years, 23 DFS events were detected. Recurrences occurred in 9 patients; 4 women (1%) had a distance recurrence and 5 (1.2%) had a local/regional recurrence. New cases of contralateral breast cancer were detected in six patients (1.5%) and eight deaths (2%) were recorded, although no recurrence was documented in the deceased patients.
Overall 7-year DFS was 93.3% (95% CI, 90.4-96.2). When patients were stratified according to hormone status, 7-year DFS was 94.6% among patients with hormone receptor–positive disease (95% CI, 91.8-97.5) and 90.7% among patients with hormone receptor–negative disease (95% CI, 84.6-97.2).
The recurrence-free interval at 7 years was 97.5% (95% CI, 95.9-99.1). Breast cancer-specific survival was 98.6% (95% CI, 97-100) and 7-year OS was 95% (95% CI, 92.4-97.7).
The researchers also conducted PAM50 testing in 227 patients. More than half of patients tested (n = 142; 63%) had tumors that were HER2-enriched; 11% had luminal B tumors (n = 26), 10% had luminal A tumors (n = 22) and 9% (n = 20) were basal-like.
The positive results seen in this analysis confirm earlier results from the APT trial. Tolaney and colleagues published 3-year follow-up data in 2014 demonstrating that adjuvant paclitaxel and trastuzumab was associated with an early risk of recurrence of about 2% among women with predominately stage 1, HER-2–positive disease.
“These data suggest that paclitaxel and trastuzumab as adjuvant therapy for node-negative, HER-2–positive breast cancer is associated with few recurrences and only four distant recurrences with longer follow-up,” the researchers wrote. “Based on these data, if chemotherapy/trastuzumab is given to a patient with stage I, HER-2–positive breast cancer, the paclitaxel-trastuzumab regimen should be considered a standard treatment.” – by Julia Ernst, MS
Tolaney SM, et al. Abstract 511. Presented at: ASCO Annual Meeting; June 2-6, 2017; Chicago.
Disclosures: Tolaney reports receiving research funding through her institution from Exelixis, Genentech/Roche, Lilly, Merck, Novartis and Pfizer.