A new finding of long-term results shows that adding pembrolizumab, sold under the brand name Keytruda, to first-line chemotherapy for women with metastatic triple-negative breast cancer (TNBC) increased the median survival time from 16.1 months to 23 months in patients with a certain type of tumor. This increased survival rate was only seen in people who had tumors with a combined positive score (CPS) for PD-L1 expression of ≥10.
PD-L1 is a type of protein that helps keep your body's immune system under control. It's sometimes found in higher amounts in cancer cells. When it binds to another protein called PD-1, it can keep your body's T-cells from killing cancer cells. Pembrolizumab stops PD-L1 from binding to PD-1, which lets your T-cells kill the cancer cells. Based on these results, the pembro-chemo combo is the new standard of care for people with those types of tumors.
The increase in survival rates was seen in patients with these types of tumors regardless of what type of chemotherapy was used with pembrolizumab. Previously, results of trials showed increased progression-free survival (PFS) rates, which is how long people live with a disease without it getting worse. Those results led to the FDA granting accelerated approval to pembrolizumab in November 2020. The new results led to the drug being granted full approval.
Pembrolizumab is currently the only type of immunotherapy approved for the treatment of triple-negative breast cancer. Another medicine, atezolizumab, under the brand name Tencentriq, was also granted accelerated approval by the FDA; however, a further trial failed to show any benefit with atezolizumab, so the manufacturer voluntarily withdrew it as a treatment option for TNBC in August 2021. In April of 2021, a committee that advises the FDA recommended that atezolizumab remain as a treatment option, so women with TNBC who were stable on atezolizumab were allowed to continue taking it, but new patients won't be started on it.