(Reuters) – Merck & Co said a phase 3 trial of cancer drug Keytruda in combination with chemotherapy showed an increase in┬áthe amount of time patients lived with small cell lung cancer without it getting worse, but did not extend overall survival.

While the blockbuster drug showed improvement in overall survival for patients treated with Keytruda in combination with chemotherapy, it did not meet statistical significance, the company said on Monday.

Keytruda has been approved to treat non-small cell lung cancer, which accounts for around 85% of lung cancer cases, and currently holds a dominant position in that market.

Small cell lung cancer (SCLC) accounts for about 10% to 15% of all cases of lung cancer, Merck said. It said the five-year survival rate for patients diagnosed in the U.S. with any stage of SCLC is estimated to be 6%.

Keytruda, Merck’s most important growth driver, has racked up U.S. approvals to treat numerous cancer types since it was first approved for advanced melanoma in 2014.

(Reporting by C Nivedita in Bengaluru and Michael Erman in New York; Editing by Shounak Dasgupta)

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