UPDATE 3-Bristol-Myers sees new route to immunoncology success in trial

* Says tumor mutation burden succeeds as new biomarker

* Bristol-Myers' shares up in premarket trade, rivals down

* Fourth-quarter profit tops estimates on demand for Opdivo (Recasts headline, first paragraph to focus on immunotherapy)

Feb 5 (Reuters) - Bristol-Myers Squibb Co said it found a new way to identify cancer patients who are treatable by its immunotherapy drugs Opdivo and Yervoy in its closely watched late-stage lung cancer trial.

Its shares rose up to 3 percent on Monday.

The company, which also reported better-than-expected quarterly earnings, said that non-small-cell lung cancer (NSCLC)patients whose tumor cells had tumor mutation burden (TMB) showed a highly statistically significant improvement in progression-free survival benefit with a combination of two of its immunooncology drugs versus chemotherapy.

The trial was testing its immunotherapy Opdivo in combination with Yervoy in patients with NSCLC.

Opdivo is going head to head with rival drugs from Merck & Co, Roche and Astrazeneca in the multibillion-dollar cancer immunotherapy market. Shares in all three companies were marginally down.

"It was hugely important that this trial succeed in some way for Bristol because first-line advanced lung cancer is such an important commercial opportunity," said Brad Loncar, chief executive of Loncar Investments, which runs the Loncar Cancer Immunotherapy ETF.

"It is a much-needed win for their company and also perhaps a win for the science in general."

The NSCLC patients being tested in the trial had high tumor mutation burden, "an important biomarker for the activity of immunotherapy," Bristol-Myers said.

In the past, companies had been classifying patients on the terms of expression of a protein called PD-L1, but that had mixed success, according to Loncar.

An independent committee recommended that the study continue, based on an interim analysis for another main goal - overall survival, or helping patients survive longer while on the treatment, Bristol-Myers added.

Fourth-quarter net loss attributable was $2.33 billion compared with a year-ago profit of $894 million, as the drugmaker took a $2.9 billion charge.

Excluding one-time items, the company said it earned 68 cents per share in the quarter ended Dec. 31, analysts were expecting 67 cents, according to Thomson Reuters I/B/E/S.

Sales of Opdivo came in at $1.36 billion, above the consensus estimate of $1.29 billion.

Blood thinner Eliquis' sales rose nearly 44 percent to $1.36 billion.

The company forecast 2018 adjusted earnings per share of $3.15-$3.30. Analysts had expected $3.23 per share. (Reporting by Manas Mishra in Bengaluru and Michael Erman in New York; Editing by Martina D'Couto and Andrew Hay)