The Food and Drug Administration (FDA) has approved pembrolizumab (Keytruda) for patients with recurrent, locally advanced or metastatic squamous cell carcinoma of the esophagus whose tumors express programmed death ligand 1. The drug should be used after other treatment has failed. The FDA has also approved a companion diagnostic device to help identify patients who are appropriate candidates for this treatment.

Pembrolizumab was previously approved to treat a variety of cancers, including melanoma, non-small cell lung cancer, small cell lung cancer, head and neck squamous cell cancer, classical Hodgkin lymphoma, primary mediastinal large B-cell lymphoma, urothelial carcinoma, microsatellite instability-high cancer, gastric cancer, cervical cancer, hepatocellular carcinoma, Merkel cell carcinoma, and renal cell carcinoma.

Pembrolizumab is a programmed death 1 (PD-1) blocking antibody. PD-1 proteins are located on the surface of cells and have a role in suppressing T-cell inflammatory activity. While this effect can be potentially helpful in some autoimmune diseases, it can contribute to the immune system's failure to kill cancer cells. In animal studies, blockage of PD-1 receptors resulted in decreased tumor growth.

Pembrolizumab's efficacy was investigated in two clinical trials. KEYNOTE-181 was a randomized, open-label, active-controlled trial that enrolled 628 patients with recurrent locally advanced or metastatic esophageal cancer that had progressed during or after one prior systemic treatment for advanced or metastatic disease. Overall survival was longer in patients who received pembrolizumab than in those receiving another standard treatment (10.3 versus 6.7 months). KEYNOTE-180 was a single arm, open-label trial that enrolled 121 patients with locally advanced or metastatic esophageal cancer that had progressed during or after at least two prior systemic treatments for advanced disease. Those receiving pembrolizumab had an overall response rate of 20%. Five patients had a response duration of six months or longer; three patients had a response duration of 12 months or longer.

To treat esophageal cancer, pembrolizumab is given as a 200-mg dose infused intravenously over 30 minutes every three weeks until disease progression or unacceptable toxicity occurs, or for up to 24 months in patients without disease progression. Nurses should avoid coadministering other drugs through the same infusion line. Warnings and adverse effects are similar whether pembrolizumab is taken to treat esophageal cancer or other cancers.

For complete prescribing information for pembrolizumab, go to http://www.accessdata.fda.gov/drugsatfda_docs/label/2019/125514s055s056lbl.pdf.