Comparison of T-DM1 and trastuzumab-pertuzumab in HER2-positive breast cancer patients with residual disease after neoadjuvant therapy: a retrospective study.

Background: For HER2-positive early-stage breast cancer patients who have received neoadjuvant chemotherapy with trastuzumab and pertuzumab (HP), it remains unclear whether to intensify treatment with T-DM1 or to continue with HP therapy in the presence of residual disease identified in postoperative pathology.

Methods: This retrospective study included patients at two cancer centers in China from January 2020 to August 2022. Patients were subsequently treated with either continued HP or intensified therapy with T-DM1 for one year. A multivariable Cox proportional hazards regression model was used to identify factors influencing patient outcomes. Propensity score matching(PSM) was employed to mitigate the impact of confounding variables, and disease-free survival(DFS) between the T-DM1 and HP groups was compared.

Results: Before PSM, 114 patients were included, with 24 in the T-DM1 group and 90 in the HP group. Multivariate analysis revealed that patients in ypStage I/II had a higher DFS than those in ypStage III. In the T-DM1 group, 14 patients (58.3%) experienced thrombocytopenia, with 12 affected during cycles 2 to 4. After PSM, no statistically significant difference in DFS between the two groups (P = 0.48). The 1, 2, and 3-year DFS rates for the T-DM1 group were 94.7%, 94.7%, and 94.7%, respectively, while for the HP group, they were 100%,100%, and 89.5%.

Conclusions: In patients with HER2-positive early breast cancer who have residual disease after receiving neoadjuvant treatment with HP, the continued administration of HP can achieve therapeutic effects comparable to those of T-DM1, without significant complications.