Expanding Treatment Options for Aggressive Breast Cancer

The FDA approved the use of an immunotherapeutic in combination with chemotherapy to treat certain patients with triple-negative breast cancer.

The U.S. Food and Drug Administration (FDA) approved the use of the immune checkpoint inhibitor pembrolizumab (Keytruda) in combination with chemotherapy to treat patients with locally recurrent unresectable or metastatic triple-negative breast cancer whose tumors test positive for a protein that helps cancer cells evade detection by the immune system. The FDA also approved a companion diagnostic test, PD-L1 IHC 22C3 pharmDx, to identify patients eligible for the combination treatment.

Pembrolizumab is an immunotherapeutic treatment that keeps immune cells active by preventing PD-L1, a protein on cancer cells, from engaging the PD-1 receptor on immune cells. This process takes the brakes off the immune system, allowing it to destroy the cancer. The PD-L1 IHC 22C3 pharmDx is a laboratory test that uses a staining process to identify the presence of PD-L1 in tissue samples of patients with a variety of cancers who may be eligible for treatment with pembrolizumab.

The approval was based on results from a multicenter, double-blind, randomized, placebo-controlled clinical trial that showed patients treated with pembrolizumab in combination with chemotherapy had greater progression-free survival than patients who received a placebo plus chemotherapy. The median time of progression-free survival was 9.7 months for those in the pembrolizumab plus chemotherapy arm versus 5.6 months for those in the placebo group. 

Breast cancer is the most common cancer among women in the U.S. and worldwide. According to federal estimates, in 2020 there will be more than 276,000 new cases and over 42,000 deaths from the disease. Triple-negative breast cancer is one of the major subtypes of breast cancer and accounts for approximately 10 percent of all cases. And triple-negative breast cancer has a higher death rate than other subtypes of the disease due in part to the limited number of treatment options. 

Triple-negative breast cancer derives its name from the absence of three receptors found on cancer cells in other subtypes. Patients with other forms of the disease may benefit from therapeutics designed to act on those receptors.  

The FDA granted accelerated approval for the use of pembrolizumab in combination with chemotherapy and the use of the PD-L1 IHC 22C3 pharmDx diagnostic test on November 13, 2020. Accelerated approval means continued approval may be contingent upon a confirmatory trial.