The U.S. Food and Drug Administration approved AstraZeneca PLC's Imfinzi as the first drug to reduce the risk of cancer progression among certain patients with stage 3 non-small cell lung cancer.

Imfinzi was approved to lower the risk of cancer spreading in patients whose tumors are not able to be surgically removed and whose cancer has not progressed after treatment with chemotherapy and radiation.

Imfinzi, or durvalumab, targets the PD-L1 protein, which is found on the surface of tumors cells and is known to help them evade body's immune system. It would be an additional therapy that can stop cancer from progressing for a longer time after chemotherapy and radiation, the FDA said in a statement.

The FDA granted the drug priority review status and breakthrough therapy designation in 2017.

Lung cancer is the leading cause of cancer-related death in the U.S., with an estimated 222,500 new diagnoses and 155,870 deaths in 2017, the FDA stated, citing the National Cancer Institute.

The approval is based on a trial that showed that cancer stopped growing for 16.8 months among patients given Imfinzi, compared to 5.6 months for those given placebo.

Imfinzi is already approved in the U.S. for treating locally advanced or metastatic urothelial carcinoma, the most common type of bladder cancer.