* Chance to lead in first-line lung cancer immunotherapy
* Key clinical trial data on drug combination Thursday
* Roche CEO sees shake-out in crowded cancer R&D field (Adds sales forecasts, further details)
By Ben Hirschler
LONDON, Dec 6 (Reuters) - After lagging rivals in cancer immunotherapies, Swiss drugmaker Roche hopes to leap-frog into the lead in the biggest market, tackling previously untreated lung cancer.
"We have a real chance to be at the forefront here," Chief Executive Severin Schwan said on Wednesday. "Our ambition is to become a clear leader in the field of cancer immunotherapies."
At the same time he warned many investors would lose money across the industry as a large proportion of the hundreds of cancer trials now underway failed, leaving just a few winners.
His optimism for Roche has been buoyed by study results showing its immune-boosting medicine Tecentriq given with chemotherapy and the older drug Avastin significantly cut the risk of lung cancer worsening.
Researchers will detail the scale of that benefit, versus chemotherapy and Avastin alone, in a keenly awaited presentation at a medical meeting in Geneva on Thursday.
"We have the potential to get into the lead in first-line lung cancer," Schwan said. "In all likelihood we have a medicine here that will potentially change the standard of care ... but we will also have to see how it compares with other therapies."
Overall survival (OS) data will also be crucial in determining the ultimate winner in lung cancer - by far the biggest oncology market - since one of the main benefits of using immunotherapy is its long-lasting effects.
Roche does not yet have that OS data but initial observations are "encouraging" and it expects results in the first half of 2018, well ahead of OS findings with a competing drug combination including chemotherapy from Merck & Co.
Roche and Merck have led the way in pioneering so-called "chemo-combo" treatment, while AstraZeneca and Bristol-Myers are betting mainly on mixing two immunotherapies, although AstraZeneca failed to show any initial benefit with this approach in a high-profile trial in July.
Currently, Tecentriq's sales - expected to total around $500 million this year - are well behind the $3.7 billion and $4.8 billion expected respectively in 2017 for Merck's Keytruda and Bristol's Opdivo, the current market leaders.
But analysts at Jefferies believe Tecentriq could sell $6.2 billion by 2021, bolstered by its promise in drug cocktails.
Tecentriq is one of several new drugs Roche is relying on to be a success to help replace revenue from older biological cancer drugs whose patents have expired or will shortly, exposing them to cheaper so-called biosimilar competition.
"On the pipeline side, we're even more de-risked than a year ago ... but there is no doubt that the impact from biosimilars will be significant," Schwan told Reuters.
"On balance, I'm now very confident that we should be able to compensate for this erosion."
Cancer research is today the hottest area of drug research, with dozens of companies conducting hundreds of clinical trials, many of which Schwan said would fail.
"There will be an enormous drop-out from all these clinical trials, which means a lot of people that invested into these trials will lose money." (Reporting by Ben Hirschler; Editing by Alexander Smith and Edmund Blair)