(Adds detail about separate haemophilia drug trial, premarket shares, additional Tecentriq details)
ZURICH, Dec 7 (Reuters) - Adding Roche's immunotherapy Tecentriq to older drugs doubled the percentage of lung cancer patients who survived a year without their disease advancing, an outcome some experts labeled unprecedented.
Thirty-seven percent of patients in a closely watched clinical trial who got Tecentriq, Avastin and chemotherapy reached the one-year mark without their cancer progressing (PFS), according to data released on Thursday.
For patients getting only Avastin and chemotherapy, that fell to 18 percent.
Roche's November announcement that its Impower 150 trial had broadly succeeded in first-line lung cancer patients helped spur a one-day, $12 billion rally in the Basel-based drugmaker's market capitalisation.
Thursday's release of specific numbers at a European Society for Medical Oncology meeting in Geneva could further fan investor optimism the Swiss drugmaker is gaining on rivals Merck & Co and Bristol-Myers Squibb.
Roche Chief Executive Severin Schwan sees an opportunity to leap-frog ahead as competitors still await their own lung cancer combination trial results.
"This is very, very promising," Dr Solange Peters, the head of Medical Oncology at the Centre Hospitalier Universitaire Vaudois in Lausanne, Switzerland, said on the latest results.
"Doubling PFS (progression-free survival) at one year is something we have not seen with any targeted therapy in unselected patients to date."
In a second significant trial result, Roche also released positive interim data from its recently approved haemophilia drug Hemlibra dosed at every four weeks, saying the results were consistent with previous studies of the medicine dosed once weekly or every two weeks.
Roche said it would submit the results from both studies to regulatory authorities around the world.
Roche shares, which are up about 5 percent this year, were seen rising 2.1 percent in premarket indicators.
It is counting on Tecentriq to help replace revenue from its $20 billion-per-year trio of Avastin, Herceptin and Rituxan whose patents have expired or will shortly, exposing them to cheaper competition.
Lung cancer is easily the biggest oncology market, with about 220,000 people in the United States due to be diagnosed this year and 155,000 seen dying from the disease often caused by smoking.
In Roche's 1,202-patient study, Tecentriq cut the risk of disease progression by 38 percent, within the range analysts have said would signify a robust result.
Patients getting Roche's immunotherapy survived an average of 8.3 months without their disease getting worse, compared with a PFS of 6.8 months for those getting chemotherapy and Avastin.
For a set of patients who expressed a specific biomarker called "Teff" that Roche is exploring to help identify people who may respond best, the results were more robust, with a 49 percent risk reduction and PFS at 11.3 months for the Tecentriq group versus 6.8 months.
Roche, which said no new safety problems cropped up, is still awaiting Impower 150's overall survival data in the first half of 2018.
Still, the trial's head, Dr Martin Reck of Germany's Lung Clinic Grosshansdorf, said those numbers "look encouraging".
Tecentriq is already approved in bladder cancer treatment and for lung cancer patients who have failed chemotherapy.
(Reporting by John Miller; Editing by Ben Hirschler and Mark Potter)