A new cancer treatment resulted in remission for every single patient enrolled in a clinical trial at the Memorial Sloan Kettering Cancer Center.

Eighteen rectal cancer patients took a new drug from GlaxoSmithKline rather than face brutal treatments like chemotherapy and life-changing surgery, and all eighteen saw their tumors completely disappear, according to the trial results published Sunday in the New England Journal of Medicine (NEJM). It is believed to be the first trial ever conducted in which all subjects became completely cancer-free.

There were no signs of a remaining tumor when the patients were given physical exams, endoscopies, PET scans and M.R.I.’s at the trial’s conclusion. None of the patients reported adverse reactions to the drug, which is rare in treatments of its type. About 20% of patients who are treated with checkpoint inhibitors, like GlaxoSmithKline’s dostarlimab, have some kind of adverse reaction, according to The New York Times.