Immunotherapy improves survival in patients with metastatic breast cancer

An immunotherapy-chemotherapy combination improved both progression-free survival (PFS) and overall survival (OS) in patients with untreated metastatic triple-negative breast cancer (TNBC), according to a study reported here.

Overall, the combination of atezolizumab (Tecentriq) and nab-paclitaxel (Abraxane) led to a modest improvement in median PFS of 7.2 months versus 5.5 months with nab-paclitaxel and placebo. The advantage increased to 2.5 months in the subset of patients with PD-L1-positive tumors at 7.5 versus 5.0 months.

Median OS increased from 17.6 months in placebo group to 21.3 months with the addition of the PD-L1 inhibitor. Patients with PD-L1-positive tumors had a more robust improvement in OS with the addition of atezolizumab (25.0 months versus 15.5 months), reported Peter Schmid, MD, of St. Bartholomew’s Breast Cancer Center in London, at the European Society for Medical Oncology congress.

The study was published simultaneously in the New England Journal of Medicine.

« These results will change the way triple-negative breast cancer is treated, » Schmid said. « Atezolizumab in combination with nab-paclitaxel is the first targeted treatment to improve survival in metastatic triple-negative breast cancer. It is also the first immune therapy to improve outcome in this cancer. »

Marlene Kok, MD, of The Netherlands Cancer Institute in Amsterdam, agreed with Schmid that results of the IMpassion30 trial « will probably change the treatment landscape for our metastatic triple-negative breast cancer patients. »

« While the benefit, in terms of progression-free survival, was relatively small, the gain in overall survival in the PD-L1-positive subgroup was impressive, » said Kok, who noted that about 40% of the patients in the trial had PD-L1-positive tumors.

Focusing on the median PFS in trials of cancer immunotherapy can be misleading, said Schmid. Anti-PD-1 therapy often produces long-lasting responses, which are not accurately reflected in median PFS values. The prolonged responses have the effect of « raising the tail » of survival curves. The reduction in the PFS hazard ratio with the addition of atezolizumab — 20% in the overall population and almost 40% in the PD-L1-positive subgroup — is a more useful statistic to gauge the impact of immunotherapy on PFS, he said…