Combining an immunotherapy drug with chemotherapy nearly doubled the survival time of some lung cancer patients compared to patients treated with chemotherapy alone, new research published Monday in the New England Journal of Medicine showed.

For the first time, a treatment that boosts the immune system greatly improved survival in people newly diagnosed with the most common form of lung cancer. It's the biggest win so far for immunotherapy, which has had much of its success until now in less common cancers.

In the study, Merck's Keytruda given with standard chemotherapy, cut in half the risk of dying or having the cancer worsens, compared to chemo alone after nearly one year.

Keytruda is called a checkpoint inhibitor. It removes a cloak that some cancer cells have that hides them from the immune system.

After one year, 69 percent of people originally assigned to Keytruda were alive versus 49 percent of the others - a result that experts called remarkable.

The Keytruda combo also delayed the time until cancer worsened - an average of nine months versus five months for the chemo-only group.

That's a big difference for such an advanced cancer, said Dr. Alice Shaw, a Massachusetts General Hospital lung cancer expert and one of the conference leaders. "This is really a pivotal study… a new standard of care," said Shaw.