Ado-trastuzumab emtansine (T-DM1) in HER2+ advanced breast cancer patients: does pretreatment with pertuzumab matter?

Aim: We evaluated the outcomes of patients treated with ado-trastuzumab emantasine (T-DM1) after first-line pertuzumab/trastuzumab, compared with those receiving a trastuzumab-only-based regimen. Patients & methods: Patients who received second-line T-DM1 after pertuzumab/trastuzumab (n = 34) were compared with those who received only trastuzumab (n = 73). Results: Overall response rate was 33.3% in patients with prior pertuzumab and 57.1% in the remaining subjects. Disease control rate was 47 and 43%, respectively, and the clinical benefit rate was 43.3 and 71.1%, respectively. Median progression-free survival was 5.0 and 11.0 months, respectively (hazard ratio: 2.02; 95% CI: 1.14-3.58; p = 0.01). Conclusion: Patients treated with T-DM1 who previously received pertuzumab present poorer clinical outcomes compared with those receiving a trastuzumab-only-based regimen in the first-line setting.