Breast Cancer Coverage from Every Angle

Atezolizumab in Metastatic Triple-Negative Breast Cancer: Long-Term Outcomes

By: Kayci Reyer
Posted: Monday, November 26, 2018

A phase I study published in JAMA Oncology found the PD-L1 inhibitor atezolizumab to be a safe and active treatment for patients with metastatic triple-negative breast cancer. Based on long-term follow-up (median of 25.3 months), Leisha A. Emens, MD, PhD, of the Hillman Cancer Center at the University of Pittsburgh, and colleagues reported “durable clinical benefit in patients with stable or responding disease and in earlier lines of treatment.”

The study included 116 women with metastatic triple-negative breast cancer who underwent treatment with atezolizumab every 3 weeks. The median duration of response was 21 months. Overall, 63% of patients experienced treatment-related adverse events, with 79% of such events being grade 1 to 2. The majority of adverse events occurred during the first year of treatment. “The safety profile was consistent with that of atezolizumab in other tumor types,” the researchers noted.

Overall response rates were higher for patients treated in the first-line setting (24%) than for those treated in the second-line or beyond setting (6%); the median overall survival was also higher for first-line patients (17.6 months) than for patients on later lines of treatment (7.3 months). The median progression-free survival was 1.4 months on Response Evaluation Criteria in Solid Tumors and 1.9 months on criteria based on immune response. The median overall survival was 15.9 months for patients with stable disease and 7.3 months for patients with progressive disease. PD-L1 expression 1% or greater was independently associated with higher overall response rates and longer overall survival.

“Early clinical data support this strategy, and phase 3 studies are already under way to evaluate the addition of chemotherapy to atezolizumab,” Dr. Emens and colleagues concluded.

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