Health researchers are increasingly studying “exceptional responders” — rare cancer patients who respond well to chemotherapy drugs that don’t help most people — for clues to designing better tumor-killing medications.

The Washington Post reports that inexplicable reversals have always existed in medicine, but until recently, such cases were considered little more than hopeful anecdotes.

That could be changing. A growing number of researchers are using emerging technologies such as genetic sequencing to figure out what makes such patients’ tumor respond to treatment and whether those factors could offer clues that might help other patients.

Last fall, the National Cancer Institute launched a nationwide search for people with a variety of cancers who had unique responses to treatments. It has already identified scores and is hoping to identify many more, the Post reports.

“What we’re trying to do with these cancers is find their Achilles’ heel and attack that,” said Barbara Conley, associate director of NCI’s Cancer Diagnosis Program.

The goal is to identify genetic biomarkers that could lead toward better treatments for other patients, involving drugs that were abandoned in early-phase trials because they didn’t work for most participants or approved medications that might benefit more patients than doctors realized.