An immunologic drug has gotten the Food and Drug Administration's stamp of approval to be used as a lung cancer treatment. This means the drug will be considered a viable option that will be offered before having to resort to chemotherapy.

The drug was approved after researchers from two separate studies found the treatment to be a breakthrough.

The drug, Keytruda, will be used to treat America’s number one cancer killer, non-small metastatic lung cancer (NSCLC).

Keytruda works by kicking the immune system into gear to fight cancer.

"This study may change current practice for the treatment of patients with advanced NSCLC,” said Johan Vansteenkiste, a Belgium medical professor, referring to one of the studies, which was published in the  New England Journal of Medicine.

There were 305 patients who were treated with Keytruda. Their illness was profession-free by four months and 80 percent of the patients were alive at six months, compared to the 72 percent of patients  who were alive after chemotherapy. Immunotherapy is already successfully used with multiple kinds of cancer, including head and neck, kidney, bladder, Hodgkin lymphoma and melanoma.

However, the approval for first-line use in treating lung cancer is one of the biggest endorsements for immunotherapy yet.

Lung cancer is the most fatal cancer in the world, and it’s responsible for 25 percent of the cancer related deaths in the U.S.

In fact, more people die of lung cancer each year than those who die from colon, breast, and prostate cancers combined.

Keytruda isn’t suited for all lung cancer patients however. It’s designed for about 30 percent of patients with tumors that show a high expression of protein marker called PD-L1, which indicates the drug will likely work.

Immunotherapy got a lot of buzz after it was credited with saving former President Jimmy Carter’s life. Carter took it after a metastatic melanoma spread to his brain.

The FDA has also loosened the restrictions on who qualifies for this therapy, opening it up as a second line treatment, post chemotherapy.

To learn more about this treatment, read CNN’s report.