Every patient in a small clinical trial saw their cancer disappear after receiving an experimental immunotherapy treatment, according to researchers.
A trial involving patients with locally advanced rectal cancer saw six months of treatment with a drug called dostarlimab.
The cancer went into remission in all the 12 patients and was then said to be undetectable through endoscopy, physical examinations and scans.
Dr Luis Diaz, one of the lead authors and an oncologist at the Memorial Sloan Kettering Cancer Center, told The New York Times: "This is the first time this has happened in the history of cancer."
Despite the results, scientists emphasised they are not calling it a cure with further study and analysis being needed - but the cancer has not returned in any of the patients since the trial ended.
The drug from the pharmaceutical company GlaxoSmithKline is used in the treatment of endometrial cancer and was given to each patient in the New York-led trial every three weeks.
