Merck & Co. Inc. said a combination of its blockbuster drug Keytruda and chemotherapy significantly improved the time certain lung cancer patients lived without their disease worsening compared to chemotherapy alone.

However, Keytruda failed to significantly improve the time patients lived since the start of treatment, also called overall survival, compared to just chemotherapy.

Results of the late-stage study showed the drug arm met one primary goal of the study by showing improvement in patient's survival duration without progression of cancer.

The Kenilworth, N.J.-based pharmaceutical giant was evaluating the Keytruda-chemotherapy combination as an initial treatment for patients with extensive-stage small cell lung cancer during the phase 3 trial called Keynote-604.

Small cell lung cancer is a fast-growing disease that spreads very quickly and can create large tumors. The disease is categorized as an extensive stage when cancer spreads widely throughout the lung, to the other lung, to lymph nodes on the other side of the chest or to other parts of the body.

Merck will discuss the results of the trial with regulatory bodies and will present them at an upcoming medical meeting.