All the patients took dostarlimab, a monoclonal antibody, every 3 weeks for 6 months. During follow-up, the cancer had disappeared on MRI scans, PET scans, biopsies, endoscopic tests, and physical exams.
“I believe this is the first time this has happened in the history of cancer,” Luis Diaz Jr., MD, the senior study author and an oncologist at Memorial Sloan Kettering Cancer Center in New York City, told The New York Times.
The study, which was sponsored by the drug company GlaxoSmithKline, was presented Sunday at the annual meeting of the American Society of Clinical Oncology. The study authors reported several surprises: None of the patients needed other treatments associated with rectal cancer, such as life-altering surgery or chemotherapy, and none had clinically significant complications.
“There were a lot of happy tears,” Andrea Cercek, MD, the lead study author and an oncologist at Memorial Sloan Kettering Cancer Center, told the newspaper.
Typically, about 1 in 5 patients have a bad reaction to drugs like dostarlimab, which is a checkpoint inhibitor, according to the Times. The drug reveals cancer cells to the immune system, allowing it to identify and destroy the cells. Severe complications can include muscle weakness and a hard time swallowing.
Cancer researchers agreed that the results will need to be repeated in larger studies, mainly because the small study focused on patients who had a rare genetic signature in their tumors, known as mismatch repair deficiency. The patients also had locally advanced rectal cancer, which had spread in the rectum and sometimes to the lymph nodes but not to other organs.
The results are “cause for great optimism,” Hanna Sanoff, MD, an oncologist at the University of North Carolina’s Lineberger Comprehensive Cancer Center, who wasn’t involved with the study, wrote in an editorial that went with the paper.
But the study was small, she noted, and it’ll take time to understand whether the patients will remain in remission.
“Very little is known about the duration of time needed to find out whether a clinical complete response to dostarlimab equates to cure,” she wrote.
The medication costs about $11,000 per dose, the newspaper reported. More information about the trial can be found at ClinicalTrials.gov.