Adjuvant trastuzumab with chemotherapy is effective in women with small, node‐negative, HER2‐positive breast cancer

BACKGROUND: Several large, randomized trials established the benefits of adjuvant trastuzumab with chemotherapy. However, the benefit for women with small, node-negative HER2-positive (HER2+) disease is unknown, as these patients were largely excluded from these trials. Therefore, a retrospective, single-institution, sequential cohort study of women with small, node-negative, HER2+ breast cancer who did or did not receive adjuvant trastuzumab was conducted. METHODS: Women with ≤ 2 cm, node-negative, HER2+ (immunohistochemistry 3+ or fluorescence in situ hybridization ≥ 2) breast cancer were identified through an institutional database. A "no-trastuzumab" cohort of 106 trastuzumab-untreated women diagnosed between January 1, 2002 and May 14, 2004 and a "trastuzumab" cohort of 155 trastuzumab-treated women diagnosed between May 16, 2005 and December 31, 2008 were described. Survival and recurrence outcomes were estimated by Kaplan-Meier methods. RESULTS: The cohorts were similar in age, median tumor size, histology, hormone receptor status, hormone therapy, and locoregional therapy. Chemotherapy was administered in 66% and 100% of the "no trastuzumab" and "trastuzumab" cohorts, respectively. The median recurrence-free and survival follow-up was: 6.5 years (0.7-8.5) and 6.8 years (0.7-8.5), respectively, for the "no trastuzumab" cohort and 3.0 years (0.5-5.2) and 3.0 years (0.6-5.2), respectively, for the "trastuzumab" cohort. The 3-year locoregional invasive recurrence-free, distant recurrence-free, invasive disease-free, and overall survival were 92% versus 98% (P = .0137), 95% versus 100% (P = .0072), 82% versus 97% (P < .0001), and 97% versus 99% (P = .18) for the "no trastuzumab" and "trastuzumab" cohorts, respectively. CONCLUSIONS: Women with small, node-negative, HER2+ primary breast cancers likely derive significant benefit from adjuvant trastuzumab with chemotherapy.