The immunotherapy drug saw 12 rectal cancer patients entering remission over six months

An experimental cancer drug appears to have cured every single patient involved in a small clinical trial, based in the US.

The 12 rectal cancer patients entered remission after taking dostarlimab over a six-month period, according to a study published in The New England Journal of Medicine. The trial was sponsored by GSK.

Dostarlimab is an immunotherapy drug, used in the treatment of endometrial cancer, but this was the first clinical investigation into whether it could be effective against rectal cancer tumours. The drug works by unmasking cancer cells, allowing the immune system to identify and destroy them.

In the trial, the 12 patients received dostarlimab every three weeks for six months. This treatment was to be followed by standard chemoradiotherapy and surgery. However, six months after the patients stopped taking the medication, their cancer had vanished, and was undetectable in all physical exams such as endoscopy, positron emission tomography (PET), or MRI scans. This is the first time that an experimental drug has been able to completely eliminate cancer cells.

When the patients were examined after treatment, they were all found to be in remission. According to the paper, all 12 had a “clinical complete response, with no evidence of tumour on magnetic resonance imaging”. None of the patients has needed further treatment, and also did not show any significant side effects.

Though the trial shows a great deal of promise for cancer patients, its small scale means that further studies are needed to draw conclusions about dostarlimab as a treatment.

“This is the first time this has happened in the history of cancer,” Dr Luis Diaz, one of the lead authors of the paper and an oncologist at the Memorial Sloan Kettering Cancer Centre in New York, US, told The New York Times.

Dr Hanna Sanoff, of the University of North Carolina, US, who was not involved in the research, said the study was “small but compelling”.

“These results are cause for great optimism,” Sanoff wrote in an editorial accompanying the paper, adding that the research had “provided what may be an early glimpse of a revolutionary treatment shift”. However, Sanoff warned that “such an approach cannot yet supplant our current curative treatment approach”, adding that it remains unclear whether the patients are cured.