Retrospective study of real-world outcomes of early stage HER2-positive breast cancer with adjuvant paclitaxel and trastuzumab

Adjuvant weekly paclitaxel and trastuzumab (APT regimen) is the standard treatment for most stage I HER2-positive breast cancer patients based on the results of the phase 2 APT trial. Conformation of long-term outcomes in real-world cohort is important. A retrospective study at the University of Padova (Italy) evaluated the APT regimen for early HER2-positive breast cancer. The study included 276 patients; most presented with HR-positive tumors (75%) and grade 3 tumors (65,6%). The majority had pT ≤ 2 cm (92.4%) and no nodal involvement (93.1%): only 6.9% had N1mic. Anatomical stage was IA in 86.2%, IB in 6.2%, and IIA in 7.6%). At a median follow-up of 4.4 years, the 3-year recurrence-free survival rate was 97.3% (95% CI 95.1-99.5), the 3-year distant relapse-free survival rate was 98.2% (96.4-100), and the 3-year invasive breast cancer-free survival rate was 97.1% (94.7-99.5). A statistically significant difference in recurrence-free survival was observed according to anatomical stage. The authors conclude that this real-world study confirms that the APT regimen is associated with excellent outcomes in stage IA HER2-positive breast cancer, while caution is warranted for patients with stage IB or IIA disease.