ASCO 2019: Metastatic Breast Cancer Updates

The meeting included several updates on BCRF-supported studies on metastatic breast cancer.

The 55th annual meeting of the American Society of Clinical Oncology was held from May 31 through June 4 in Chicago. This year’s meeting included several updates in metastatic breast cancer research. Below are key highlights in this important field.

ER-positive/ HER2-negative breast cancer. CDK4/6 inhibitors plus anti-estrogen therapy continue to demonstrate significant survival benefit in patients with hormone receptor-positive, HER2-negative advanced breast cancer.

Three CDK4/6 inhibitors, palbociclib (Ibrance®), ribociclib (Kiqali®), and abemaciclib (Verzenio®) have been FDA-approved for treatment in combination with anti-estrogen (endocrine therapy) in post-menopausal women.

Two trials testing anti-CDK 4/6 drugs, ribociclib and palbociclib, respectively in patients with pre-menopausal advanced breast cancer showed that younger women received similar benefit from the anti-estrogen CDK4/6 combination as was reported for post-menopausal patients. Both drugs are approved for treatment in pre-menopausal women.

In discussing the presentations, BCRF investigator, Dr. Angelo De Leo, drew from previous studies to highlight that sensitivity to endocrine therapy may be driving the benefit of CDK4/6 inhibition. In previous studies of CDK4/6 inhibition, the greatest benefit was seen in patients whose tumors were sensitive to endocrine therapy. In the current studies, women had not been previously treated with endocrine therapy, so their tumors would not have yet built up resistance. Ongoing studies are testing a biomarker that may be able to select patients most likely to benefit from this combination approach.

Triple-negative breast cancer. The Impassion 130 study was the first to show a significant benefit of the addition of immune-targeted therapy (atezolizumab) to chemotherapy in patients with advanced triple-negative breast cancer (TNBC). At this year’s meetings, researchers reported updates from the study confirming earlier findings of extended benefit of immune therapy plus chemotherapy in this patient population.

In previous reports, BCRF investigator, Dr. Leisha Emens, explained the greatest benefit was seen in patients with PD-L1-positive tumors, specifically tumor infiltrating immune cells with high PD-L1, the molecular target of atezolizumab. An updated overall survival analysis reported at ASCO had a median of 18 months of follow up. Results from the second analysis were consistent with earlier findings.

Patients with PD-L1 positivity had median overall survival of 25 months with atezolizumab versus 18 months in similar patients who did not receive atezolizumab. The authors reported that the atezolizumab plus chemotherapy regime was generally well tolerated and side effects were well controlled. Patient surveys were similar between the two groups.