Shares of Merck & Co. Inc. MRK, -2.15% surged 2.6% in premarket trade Monday, after the drug maker said its cancer treatment Keytruda met the primary endpoint of a phase 3 trial evaluating the Keytruda as monotherapy for the first-line treatment of metastatic non-small cell lung cancer. The primary endpoint was overall survival. An independent data monitoring committee (DMC) determined that treatment with Keytruda resulted in significantly longer overall survival than platinum-based chemotherapy in tested patients. Based on the DMC's finding, the trial will continue to evaluation progression-free survival, which is the secondary endpoint. Merck's stock has lost 5.2% year to date through Monday, while the SPDR Health Care Select Sector ETF XLV, -2.41% has shed 3.4% and the Dow Jones Industrial Average DJIA, -2.34% has slipped 3.2%.