Trastuzumab emtansine versus trastuzumab plus pertuzumab for HER2-positive breast cancer with residual disease after neoadjuvant therapy: a real-world study.

Objective: To evaluate the efficacy and safety of T-DM1 versus trastuzumab plus pertuzumab in adjuvant treatment of HER2-positive breast cancer patients with residual invasive disease after neoadjuvant therapy. Methods: This study retrospectively analyzed 184 patients treated at Renmin Hospital of Wuhan University from January 2019 to January 2022. The patients were divided into a T-DM1 treatment group and a dual-target treatment group based on whether they received T-DM1 or trastuzumab plus pertuzumab during adjuvant therapy. Clinical and pathological data of the two groups were collected before and after surgery, and follow-up was conducted. The primary study endpoint was disease-free survival (DFS). Results: Disease progression occurred in 20.3% of the dual-target treatment group and 12.6% of the T-DM1 treatment group. Although T-DM1 was associated with a 38% reduction in recurrence risk, the difference was not statistically significant (HR: 0.62, 95% CI: 0.30-1.26, P = 0.19). Exploratory subgroup analyses suggested improved DFS with T-DM1 in patients with initially unresectable disease, preoperative lymph node positivity, or poor pathological response (MP 1-3 or RCB III); In terms of safety, both groups of patients were consistent with the known safety profile. No treatment-related deaths occurred. Grade ≥3 thrombocytopenia was significantly more frequent with T-DM1 (8.45% vs 0.88%, P = 0.01), representing a clinically important toxicity trade-off. Conclusion: The use of T-DM1 in the adjuvant setting suggests improved disease-free survival in HER2-positive non-pCR patients who were initially inoperable, had preoperative lymph node positivity, or exhibited poor pathological response (MP grade 1-3 or RCB III).