Merck & Co. Inc. said Tuesday its therapy involving cancer drug Keytruda in combination with chemotherapy met the main goal of a late-stage study for treating a type of gastric cancer.

The combo therapy showed a "statistically significant" and "clinically meaningful" improvement in the study by helping cancer patients live longer, compared with chemotherapy as a standalone treatment, the drugmaker said.

The treatment also helped in improving progression-free survival of patients with the cancer, Merck said, citing the study.

Merck was testing the therapy as a first-line treatment for patients with a type of gastric cancer, or gastroesophageal junction adenocarcinoma.