NEW YORK (Reuters) - The combination of cancer drugs Tarceva and Avastin delayed the worsening of advanced lung cancer following chemotherapy longer than Avastin alone, according to results from a clinical trial.

The study was designed to test Tarceva as a so-called maintenance therapy to help delay progression of the disease following successful chemotherapy treatments. Tarceva, which is co-marketed by U.S. biotech company OSI Pharmaceuticals Incand Swiss drugmaker Roche Holding AG, is currently approved to treat advanced lung cancer after at least one prior therapy has failed.

“It’s fairly unequivocal in my mind that the Avastin/Tarceva combination is superior to either agent alone,” Dr. Vincent Miller of Memorial Sloan-Kettering Cancer Center and one of the study’s lead investigators said in an interview.

In the 768-patient Atlas study, there was a 29 percent reduction in the risk of disease progression for those patients treated with the Tarceva/Avastin combination compared to those who received Avastin plus a placebo, according to data presented Saturday at the American Society of Clinical Oncology (ASCO) meeting in Orlando, Florida.

The median progression-free survival -- the time it took for the cancer to get worse in half the patients -- was 4.8 months for the combination therapy versus 3.7 months for the placebo group, researchers said.

The study was halted early because the improvement in efficacy found in the Tarceva group was deemed to be statistically significant.

It remains to be seen how investors will view the results given the modest 1.1-month difference in progression-free survival seen with the expensive combination therapy.

“Anything more than a month warrants attention and will lead people to consider this strategy in treating their patients,” Miller said.

OSI Chief Executive Colin Goddard recently said approval as a maintenance therapy could add $500 million to annual U.S. Tarceva revenue, more than doubling sales of the oral biotech medicine.

Tarceva, known chemically as erlotinib is expected to compete with Eli Lilly and Co’s Alimta as a maintenance therapy following successful chemotherapy. The Tarceva results will likely be compared to maintenance data presented on the Lilly drug at the ASCO meeting.

A different Tarceva maintenance trial being presented at the ASCO meeting showed a 41 percent advantage over placebo in the time patients live without their disease worsening. But that study showed only a 1.1-week difference in progression-free survival, which may have been a statistical anomaly, according to OSI.

Tarceva could be approved for maintenance use in the United States by mid-January of 2010, OSI said.

No unexpected safety issues arose in the Atlas trial beyond expected levels of toxicity, researchers said.

“The combination has been extensively studied before,” Miller said. “It’s well established that this is a pretty safe, well tolerated combination.”

The next step, Miller said, will be biomarker research to determine just which patients are likely to benefit most from the Tarceva/Avastin therapy.

Avastin, a multibillion-dollar cancer drug known chemically as bevacizumab, was developed by Genentech, which is now fully owned by Roche.