- An experimental drug eliminated rectal cancer from each patient in a 12-person study.
- U.S. scientists said the complete remission in all patients was “unheard of.”
- An outside expert said the results were “convincing”, but we can’t be sure if they were cured.
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An experimental drug appeared to eliminate all patients with rectal cancer with minimal side effects in an unprecedented study, but oncologists say it is too early to make sure they are cured.
The drug, called dostarlimab, was given to 12 people with a specific type of rectal cancer every three weeks for six months in a small study at the Memorial Sloan Kettering Cancer Center in New York City.
After the course of treatment, the cancer was undetectable on physical examination, endoscopy, PET and MRI for each person, MSKCC researchers said in a presentation at the annual meeting of the American Society of Clinical Oncology on Sunday .
Participants did not need any other treatment for up to a year, on average, and there were no side effects bad enough to affect day-to-day activities, the researchers said.
Dr. Alan P. Venook, a colorectal cancer specialist at the University of California, San Francisco who did not participate in the study, told the New York Times that complete remission in each patient was “unheard of.”
Dr. Andrea Cercek, an MSKCC oncologist and co-author of the study, said there were “many tears of happiness” from trial participants when they discovered that no further treatment was needed, according to the Times.
Standard treatment includes a grueling combination of surgery, multiple chemotherapy drugs, and radiation to destroy cancer cells, often with unpleasant and permanent side effects such as nervous problems, infertility, and intestinal and sexual dysfunction.
Cercek said in a press release that the implications of standard cancer treatment on people’s quality of life were “substantial, especially in those where standard treatment would affect the potential for having children.”
“As the incidence of rectal cancer increases in young adults, this approach may have a significant impact,” Cercek said of the potential of dostarlimab.
Colorectal cancer cases among younger adults are expected to double in 2030, the MSKCC said.
Dostarlimab works by helping the immune system to identify and destroy cancer cells. The drug, called Jemperli, is already used in patients with endometrial cancer, but it was unclear if it would work for rectal malignancies. Participants in the trial had a type of rectal cancer called “mismatch repair deficiency.” About 5 to 10% of people with rectal cancer have this type of cancer, where the genes responsible for correcting any errors during cell replication are defective. The study cannot tell if dostarlimab will work in patients with other types of rectal cancer.
We don’t know if it’s a cure
Hanna K. Sanoff, an oncologist at the Lineberger Comprehensive Cancer Center at the University of North Carolina, wrote in a New England Journal editorial that it was a “contracting” study.
Sanoff warned that the result was an imperfect indicator for long-term cancer control. “Cancer regrowth occurs in between 20 and 30 percent of these patients when the cancer is managed non-surgically,” he said.
Sanoff added that it was unclear whether it would be safe to deploy the drug on a large scale because it required specific imaging techniques, such as PET scans, which are not readily available and could mean that possible tumor regrowth is being lost.
The study was also too small to show rarer side effects, Sanoff said.
Possible side effects of this drug include immune-mediated reactions in any organ, such as inflammation of the inflammation of the lungs. The most common side effects in patients who have taken the drug for endometriosis include: fatigue, nausea, diarrhea, anemia, and constipation.
“These results are a source of great optimism, but this approach cannot yet supplant our current curative treatment approach,” Sanoff said.