FDA approves immunotherapy for some rectal cancer patients — TIME

In the United States, the Food and Drug Administration (FDA) on October 19 approved dostarlimab, known by the brand name Jemperli, for the treatment of a specific type of rectal cancer. The drug was approved for patients with tumors with high microsatellite instability or deficient DNA mismatch repair — MSI-H/dMMR, TIME reports.

This type of cancer is associated with an accumulation of genetic mutations that prevent cells from properly repairing DNA damage. According to the publication, it accounts for about 5–10% of rectal cancer cases.

Study results

In a study involving 154 people with MSI-H/dMMR rectal cancer, 68% of patients had a complete clinical response after one year. This means that doctors found no signs of a tumor using imaging methods and other means of monitoring it.

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Participants received nine infusions of dostarlimab — one every three weeks for six months. Andrea Cercek, head of the colorectal cancer program at Memorial Sloan Kettering Cancer Center and the lead researcher, said that maintaining a complete clinical response for a year indicates the durability of the result.

The possibility of avoiding standard treatment

Dostarlimab belongs to checkpoint inhibitors and helps the immune system recognize and attack tumor cells. Standard treatment for rectal cancer may include chemotherapy, radiation therapy, and surgery. For some patients with the relevant mutations, the new regimen potentially makes it possible to avoid these methods if the tumor disappears after immunotherapy.

About 20% of study participants reported fatigue, rash, diarrhea, and severe itching. Cercek stressed that doctors still need to determine more precisely how to assess a complete clinical response and monitor patients after treatment. Her team is studying analysis of tumor genetic fragments in the blood and improved imaging methods.