Philip Prichard, of Memphis, has seen his renal cell cancer virtually wiped out by the immunotherapy drug nivolumab. (Lance Murphey/For the Washington Post)

CHICAGO — A new drug that unleashes the body's immune system on cancer cells performed better than a traditional chemotherapy agent in fighting an advanced form of lung cancer, researchers reported Friday. The new drug was also less toxic to patients.

Nivolumab, one of three government-approved drugs that stimulate the immune system to take on foreign invaders, improved outcomes for 19.2 percent of patients with non-squamous cell non-small cell lung cancer, compared with 12.4 percent of people who were treated with docetaxel. Patients also survived longer -- a median of 12.2 months vs. 9.4 months for those on chemotherapy, and saw a 27 percent smaller chance of death while on the drug.

Patients whose tumors released a specific kind of protein did even better in the study of 582 people, surviving 17.2 months, vs. 5.6 months for the chemotherapy group.

"There is no doubt that immunotherapy has come to stay in lung cancer," said Luis Paz-Ares of the Hospital Universitario Virgen Del Rocio in Sevilla, Spain, who led the research.

Immunotherapy works by removing the brakes or "checkpoints" that keep killer T-cells from recognizing and attacking cancer. In the past few years, it has quickly become the fourth, and perhaps most promising, avenue of cancer treatment, alongside surgery, radiation and chemotherapy.

[He had months to live before immunotherapy made his tumors disappear.]

Lung cancer is the leading cause of cancer deaths world-wide and 1.8 million people will be diagnosed with it this year, Paz-Ares said. The Food and Drug Administration approved nivolumab earlier this year for use against squamous cell non-small cell lung cancer, but this group of people is considerably larger. Paz-Ares said he expects FDA approval to use the drug on these patients soon.

Two other immunotherapy drugs are government-approved for treatment of melanoma, a lethal form of skin cancer, as is nivolumab.

Only 7 percent of the nivolumab patients suffered side effects from the medication, a smaller proportion than the 20 percent who took docetaxel. And they suffered a much smaller number of serious side effects.

The new research was presented at the annual meeting of the American Society of Clinical Oncology, where 35,000 people in the field are gathered.

In a second study presented Friday, researchers from Johns Hopkins University and elsewhere showed that genetic testing can be used to predict whether the cancers in a small percentage of people will respond to immunotherapy. The test could be valuable in determining how to use the highly expensive checkpoint inhibitor drugs, which can cost $10,000 a dose or more.

Many of the cancers examined in the study had been considered poorly responsive to immunotherapy. They included colorectal, endometrial, stomach and small bowel cancers.

But the team led by Dung T. Le, a medical oncologist at the school's Kimmel Cancer Center, showed that tumors with genetic defects that make them poor at repairing errors as DNA is synthesized mutate hundreds and perhaps thousands of times. Those mutations express a protein that can tell doctors whether the tumor will be a good candidate for immunotherapy.

Le said at a media briefing that her study is the first "to use genetics to guide immunotherapy." The small, early stage study involved 41 patients who were treated with pembrolizumab, one of the drugs the FDA has approved for treatment of melanoma.

Overall, Le said, the "mismatch repair deficiency" used to guide the therapy is present in just 4 to 5 percent of many cancer types. But in some, it may be found in as many as 40 percent of tumors. The tests cost just a few hundred dollars and in some cases may be conducted anyway, so they would not add extra costs to a patient's care, she said.