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Atezolizumab Added to T-DM1 Improves OS and PFS in HER2+ Breast Cancer

Leisha Emens, MD
Published Online:8:29 PM, Fri November 22, 2019


Leisha A. Emens, MD, PhD, professor of medicine, and co-leader of the Hillman Cancer Immunology and Immunotherapy Program, Hillman Cancer Center, University of Pittsburgh Medical Center, shares the overall survival (OS) results of the phase II KATE2 study (NCT02924883) presented at the 2019 ESMO Annual Meeting.

The addition of atezolizumab (Tecentriq) to T-DM1 (trastuzumab emtansine; Kadcyla) did not improve progression-free survival (PFS) in patients with HER2-positive breast cancer overall, in KATE2. However, the was a PFS benefit in the subgroup of patients who expressed PD-L1 in their immune cells. The improvement in PFS was clinically significant as indicated by the hazard ratio, which was 0.6. The same HR was seen with atezolizumab in the IMpassion130 trial (NCT02425891), which looked at the combination of atezolizumab and nab-paclitaxel (Abraxane) in patients with triple-negative breast cancer.

In terms of overall survival (OS), a key end point of the KATE2 study, there was a numerical improvement in OS in the overall HER2-positive patient population. The HR was 0.74. Although the overall population showed no significant difference in OS over the period of 1 year, patients whose immune cells expressed PD-L1 had a 6-percentage point improvement in OS.

The data suggest PD-L1 expression in the immune cells, as determined by the Ventana PD-L1 (SP142) assay, may be a reliable way of predicting which patients with triple-negative breast cancer and HER2-positive breast cancer could respond to atezolizumab.   
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