Outcomes of re-treatment with first-line trastuzumab plus a taxane in HER2 positive metastatic breast cancer patients after (neo)adjuvant trastuzumab: A prospective multicenter study.

Trastuzumab is the backbone of HER2-positive early breast cancer (eBC) and metastatic breast cancer (mBC) treatment, but limited data exist as to re-treatment in relapsed patients. In this prospective, single arm, multicenter trial, we assessed efficacy and safety of trastuzumab and taxane combination in Chinese patients with HER2-positive mBC relapsed after prior (neo)adjuvant trastuzumab. Patients with previous (neo)adjuvant trastuzumab treatment for≥9 weeks and a relapse-free interval ≥6 months were assigned to trastuzumab treatment with paclitaxel or docetaxel. The primary endpoint was progression free survival (PFS). Secondary endpoints included overall response rate (ORR), clinical benefit rate (CBR), duration of response (DOR), time to progression (TTP), overall survival (OS) and safety profile. Thirty-two patients were enrolled and treated for a median duration of 33.5 weeks. The median PFS was 9.9 months (95% CI, 6.28 - 13.63 months). The ORR was 81.3% (95% CI, 63.6% - 92.8%) and CBR (CR+PR+SD≥6months) was 81.3% (95% CI, 63.6% - 92.8%). The median DOR was 9.8 months (95% CI, 5.82 - 11.60 months) and median TTP was 9.9 months (95% CI, 6.28-13.63 months). OS median follow-up time was 20.1 months and 25% OS time was 25.5 months. The safety profile was acceptable with common adverse events including leukopenia (59.4%), neutropenia (56.3%), hypoaesthesia (34.4%) and granulocytopenia (31.3%). In conclusion, re-treatment with trastuzumab plus a taxane as first-line therapy is an effective regimen for patients with HER2-positive mBC relapsed after (neo)adjuvant trastuzumab. The safety profile was good and the adverse reactions were tolerable and manageable.