CHICAGO (AP) — A major study has shown that a drug targeting the body’s disease-fighting immune system may improve survival for the most common form of lung cancer.

These drugs have transformed treatment of melanoma, the deadliest skin cancer. Studies presented at a medical conference Friday in Chicago suggest these immune therapies can play a broader role in more common cancers. Lung cancer is the leading cause of cancer deaths nationwide.

The new study tested Bristol-Myers Squibb’s Opdivo (op-DEE-voh). It blocks a protein that prevents the immune system from attacking cancer cells. It worked better than chemotherapy for a form of advanced non-small cell lung cancer. Opdivo patients lived on average three months longer. It might not seem like much but advanced lung cancer is incurable and any success is considered promising.