Jan Crisitello, a 70-year-old grandmother of four, was diagnosed in 2002 with stage 4 melanoma, which kills the vast majority of its victims within five years. Although chemotherapy helped her make it past the five-year mark, by 2007 the cancer was growing again. Desperate, she joined a 29-patient trial of a drug being developed by Pfizer. The drug was a failure for almost all of the patients, and Pfizer spokeswoman Sally Beatty says it has been “deprioritized for further development.” For Crisitello, the drug worked, and her cancer is in full remission. Now oncologists are studying her DNA to determine how her genome may have made her unusually responsive to the drug. “I feel very fortunate,” she says. “It would make me feel good if they found out why and could replicate that for other people.”
As many as 1 in 10 patients respond well in clinical trials of experimental medicines that U.S. regulators end up rejecting, according to the National Cancer Institute (NCI). To understand why these patients had such a response, researchers are beginning to use DNA sequencing technology to determine if the patients they call “exceptional responders” carry gene variations that can lead to better targeted therapies, including new treatments and the reconsideration of others.
Traditional treatments such as chemotherapy kill healthy cells along with malignant ones, but targeted therapies are designed to leave healthy cells unscathed and home in on cancer cells that make tumors grow and spread. The catch is that they don’t work for everyone, and even patients who find them helpful tend to develop resistance over time. The NCI and academic medical centers including Memorial Sloan Kettering Cancer Center in New York, the Dana-Farber Cancer Institute and Massachusetts General Hospital in Boston, and the Broad Institute in Cambridge, Mass., are creating a national database of exceptional responders to aid research. “What was yesterday’s miracle event is today becoming a subject of scientific inquiry,” says Leonard Lichtenfeld, an oncologist and the deputy chief medical officer of the American Cancer Society.
So far, about 100 exceptional responders have been identified by researchers poring through roughly a decade’s worth of clinical trials, says Barbara Conley, associate director of the NCI’s cancer diagnosis program. Starting in June, she says, the institute will urge researchers and doctors nationwide to send in clinical data on these patients. “We want to cast a broad net,” Conley says. “The key is, can you find another patient with the same kind of abnormality, and will they respond?”
In a study presented in early April at the American Association for Cancer Research meeting in San Diego, researchers analyzed the case of a 57-year-old woman with advanced thyroid cancer whose tumor “melted away” during a drug trial and didn’t start growing again for 18 months, according to the study’s lead author, Dana-Farber instructor Nikhil Wagle. Although the rare, aggressive disease kills most victims within five months, an analysis of the patient’s genes showed that a mutation made her tumor responsive to Novartis’s Afinitor, a drug typically used to treat kidney or breast cancer. Researchers plan to conduct further trials with thyroid cancer patients who have similar genetic mutations, Wagle says.
One of the first exceptional responders to have her genome sequenced has a similar mutation and saw her bladder cancer go into complete remission after she took Afinitor, says David Solit, director of the Center for Molecular Oncology at Memorial Sloan Kettering. He’s been seeking out surprising cases of cancer recovery ever since, trying to identify drugs that would be effective against diseases for which they weren’t intended. “I meet with clinical teams and often see these patients who have dramatic results to compounds not moving forward because they failed in a population,” Solit says. “These are mysteries we’ve always tried to solve, but we didn’t have the tools until now to figure out the variation of responses in patients.”
The challenge is to find a drug that even an ideal patient won’t develop a resistance to, says Lecia Sequist, an oncologist at Massachusetts General Hospital and associate professor of medicine at Harvard Medical School. People with advanced melanoma such as Crisitello are usually prescribed ipilimumab, a drug sold by Bristol-Myers Squibb under the name Yervoy, but only 1 in 5 patients benefits from it, says Crisitello’s doctor, Lynn Schuchter. “While we’ve made huge advances in immunotherapy in recent years,” says Schuchter, the chief of hematology-oncology at the University of Pennsylvania’s Perelman School of Medicine, “we are still in the dark ages as to who should get the drug and why they are benefiting.”