Some Rectal Cancer Patients May Be Able to Skip Surgery, Chemo, and Radiation

—Sebastian Kaulitzki/Science Photo Library—Getty Images Immune-based treatments for cancer have become the biggest new advance in tackling tumors, and the latest approval could make a big difference for some people with rectal cancer.

On Oct.

19, the U.S.

Food and Drug Administration (FDA) approved dostarlimab (brand name: Jemperli) to treat a specific type of rectal cancer called microsatellite instability-high (MSI-H)/mismatch repair deficient cancer.

This cancer is caused by the accumulation of certain genetic mutations that prevent rectal cells from repairing DNA damage and accounts for 5-10% of rectal cancers.

In a study of 154 people with this type of rectal cancer who were treated with dostarlimab, 68% had a complete clinical response at one year, which meant doctors could not see evidence of tumors on imaging or other methods for tracking the tumors.

In the study, which the drug's manufacturer, GSK, submitted to the FDA, people received nine infusions of the drug: once every three weeks for six months.

“Not only did they reach clinical complete response, but they maintained that for a year,” says Dr.

Andrea Cercek , section head of colorectal cancer at Memorial Sloan Kettering Cancer Center and principal investigator of the study. (Some of the earliest patients have continued to remain tumor-free for even longer. ) “That really suggests that the response is durable and real.” Dostarlimab is a checkpoint inhibitor, which means it releases the brakes that hold back the immune system from recognizing and attacking tumors.

The drug allows immune cells to destroy cancer, making it a powerful weapon for seeking out cancer cells no matter where they spread or hide.

“We have completely leapfrogged over standard of care with a simple immunotherapy that melts the tumor away,” says Dr.

Luis Diaz, head of solid tumor oncology at Memorial Sloan Kettering and one of the trial investigators.

The benefits of avoiding standard rectal-cancer treatment Standard treatment for rectal cancer involves chemotherapy, radiation, and surgery to remove the rectum that requires patients to wear colostomy bags for the rest of their lives.

The dostarlimab approval means more patients whose tumors have specific mutations could avoid those aggressive therapies altogether.