T-DM1 efficacy in trastuzumab-pertuzumab pre-treated HER2 positive metastatic breast cancer patients: a meta-analysis

BACKGROUND: Current guidelines consider T-DM1 the standard 2(nd) line therapy for HER2 positive metastatic breast cancer (MBC) patients following trastuzumab (T) + pertuzumab (P) and taxane 1(st) line treatment. Despite this, there are no prospective studies supporting this sequence. METHODS: We performed a meta-analysis using real world data to determine the efficacy of T-DM1 after 1(st) line TP in HER2 positive MBC patients. We used a random-effect model to find differences in the rate of 1-year progression free survival (PFS) between TP pre-treated population and the EMILIA phase III pivotal trial. RESULTS: Seven studies were eligible. The meta-analysis showed a combined 1-year PFS risk difference for T-DM1 efficacy after TP in 2(nd) or more lines of -0.122, with lower and upper limits of -0.253 and 0.010, respectively (p = 0.07), with low heterogeneity among studies (I(2) 0.01%, p = 0.836). Considering the four studies on T-DM1 in 2(nd) line setting, 1-year PFS risk was -0.034 (95% CI -0.207 – 0,139; p = 0.701) (I(2) 0.01%, p = 0.91). CONCLUSION: Overall, the efficacy of T-DM1 after TP seems to be similar to that previously reported in the EMILIA trial. In the second line setting, data are not mature enough to confirm T-DM1 efficacy in TP pre-treated population. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12885-022-09556-7.