Outcomes of patients with small and node-negative HER2-positive early breast cancer treated with adjuvant chemotherapy and anti-HER2 therapy—a sub-analysis of the ALTTO study

Background: Patients with small node-negative HER2-positive breast cancer are commonly treated with paclitaxel and 1 year of adjuvant trastuzumab. We performed a sub-analysis of the ALTTO trial to explore the long-term outcomes of patients with small node-negative tumours. Methods: The ALTTO trial randomised 8381 patients with early HER2-positive BC treated with adjuvant chemotherapy (anthracycline/taxane- or taxane/carboplatin-based), to trastuzumab (T), lapatinib (L), their sequence (T → L) or their combination (L + T). Patients with tumours ≤3 cm and node-negative were included in this sub-analysis. Results: A total of 2821 patients were analysed (median follow-up of 7 years). The median age was 52 years, and most patients had tumours ≤2 cm (64.3%). The 7-year disease-free survival (DFS) was 88.1% (95% CI: 86.7–89.3%). DFS was similar for arms T, T + L and T⟶L and significantly lower for arm L (stratified log-rank P = 0.031). The 7-year overall survival rate was 95.9% (95% CI: [95.0–96.6%) and the 7-year time-to-distant recurrence was 93.4% (95% CI: 92.3–94.4%). Conclusion: With most patients treated with anthracycline-based regimens, ALTTO shows that patients with small tumours treated with trastuzumab and concomitant chemotherapy have excellent long-term outcomes, similar to those of the APT trial. Trial registration: Clinicaltrials.gov identifier NCT00490139.