Neoadjuvant trastuzumab (H), pertuzumab (P), and chemotherapy versus trastuzumab emtansine (T-DM1) and P in human epidermal growth factor receptor 2 (HER2)-positive breast cancer (BC): Final outcome results from the phase III KRISTINE study.

500 Background: KRISTINE compared neoadjuvant chemotherapy plus dual HER2- blockade (HP) with T-DM1 plus P (T-DM1+P), a targeted regimen that omits standard chemotherapy. T-DM1+P resulted in a lower pathologic complete response (pCR) rate, but a more favorable safety profile. Here we present the final outcomes from KRISTINE. Methods: KRISTINE (NCT02131064) was a randomized study of T-DM1+P versus docetaxel, carboplatin, and H plus P (TCHP). Patients with HER2-positive stage II–III BC received 6 cycles of neoadjuvant T-DM1+P or TCHP q3w. Patients receiving T-DM1+P continued adjuvant T-DM1+P; patients receiving TCHP received adjuvant HP, for 12 cycles in each arm. Patients in the T-DM1+P arm without pCR were encouraged to receive standard adjuvant chemotherapy before adjuvant T-DM1+P. Secondary endpoints, analyzed with descriptive statistics, included event-free survival (EFS; all events pre- and post-surgery), invasive disease-free survival (IDFS; invasive events post-surgery), overall survival and safety. Results: At median follow-up of 37 months, EFS favored TCHP (HR = 2.61 [95% CI: 1.36–4.98]), due to more locoregional progression events in the T-DM1+P arm before surgery (6.7% vs 0; Table). pCR was associated with reduced risk of an IDFS event (HR = 0.24 [95% CI: 0.09– 0.60]) regardless of treatment arm. There were 5 deaths (2.3%) in the TCHP arm and 6 (2.7%) in the T-DM1+P arm. There were more grade ≥3 AEs with TCHP but a higher rate of AEs leading to treatment discontinuation with T-DM1+P. Conclusions: EFS numerically favors TCHP due to locoregional progression events with T-DM1+P prior to surgery. T-DM1+P was associated with fewer grade ≥3 AEs but increased treatment discontinuation. Clinical trial information: NCT02131064. [Table: see text]