Long-Term Survival Analysis of Adjuvant Chemotherapy with or without Trastuzumab in Patients with T1, Node-Negative HER2-Positive Breast Cancer

Purpose: Adjuvant therapy for small, node-negative HER2-positive breast cancer (HER2(+) BC) is controversial. We aimed to identify the subgroup that would benefit most from adjuvant chemotherapy and trastuzumab. Experimental Design: We reviewed records of patients with pT1N0M0 HER2(+) BC treated at our institution from January 1, 1998, through October 31, 2009. We compared three groups: A, no adjuvant chemotherapy; B, adjuvant chemotherapy only; and C, adjuvant chemotherapy with trastuzumab. We evaluated disease-free survival (DFS), overall survival (OS), distant recurrence-free survival (DRFS), and breast cancer-specific survival (BCSS) in each group. Results: We reviewed 587 consecutive patients with a median follow-up of 123.0 months. The 10-year DFS rate was 81.0%, 65.4%, and 97.3% in groups A, B, and C, respectively (P < 0.001). The restricted mean survival time ratio did not differ between groups A and B [ratio = 0.982; 95% confidence interval (CI), 0.930-1.036; P = 0.498). Cox regression showed that adjuvant chemotherapy with trastuzumab was associated with better DFS compared with no adjuvant chemotherapy [hazard ratio (HR), 0.071; 95% CI, 0.025-0.204; P < 0.001). Larger tumor size was associated with short DFS (HR, 2.384; 95% CI, 1.549-3.056; P < 0.001); improvements in DFS, OS, DRFS, and BCSS were observed with adjuvant chemotherapy plus trastuzumab in patients with tumors >= 0.8-cm diameter. Receiving adjuvant chemotherapy with trastuzumab was not associated with improved DFS, OS, or DRFS for tumors <0.8 cm. Conclusions: Adjuvant chemotherapy plus trastuzumab should be recommended for patients with pT1N0M0 HER2(+) BC >= 0.8 cm in diameter; adjuvant therapy may not be necessary for tumors <0.8 cm.