A small NYC-led cancer trial has achieved a result reportedly never before seen - the total remission of cancer in all of its patients.

To be sure, the trial — led by doctors at Memorial Sloan Kettering and backed by drug maker GlaxoSmithKline — has only completed treatment of 12 patients, with a specific cancer in its early stages and with a rare mutation as well.

But the results, reported Sunday in the New England Journal of Medicine and the New York Times, were still striking enough to prompt multiple physicians to tell the paper they were believed to be unprecedented.

One cancer specialist told the Times it was an "unheard-of" result.

According to the NEJM paper and the Times report, all 12 patients had rectal cancer that had not spread beyond the local area, and their tumors all exhibited a mutation affecting the ability of cells to repair damage to DNA.

After being treated with the drug, dostarlimab, all 12 are now in complete remission, with no surgery or chemotherapy, no severe side effects — and no trace of cancer whatsoever anywhere in their body.

Doctors quoted by the Times said that while the results were promising, they would need to be replicated and expanded - nor was it clear if the medication in question would be useful beyond this specific application.