TUESDAY, Nov. 2 (HealthDay News) -- Researchers report that drugs used to treat diabetes may indeed both prevent and contain lung cancer.

The findings, being presented Tuesday at the annual meeting of the American College of Chest Physicians in Vancouver, back up preliminary data that some diabetes medications might protect against tobacco-induced lung cancer.

"Patients who did not develop lung cancer had a much higher chance of taking one of these medications than those who did develop lung cancer," said study author Dr. Peter Mazzone. "And those who did develop lung cancer were much less likely to have seen that cancer spread outside the chest and more likely to survive longer with one of these drugs."

Both metformin and the class of drugs known as thiazolidinediones (which includes Avandia and Actos) are used by tens of millions of Americans.

A mouse study published in September found that metformin was associated with up to a 73 percent reduction in the number of tumors mice developed when they were given a common carcinogen found in tobacco. The mice had been genetically engineered to be susceptible to this kind of tumor. Epidemiological studies in humans have found similar effects.

Metformin was originally marketed as Glucophage, but is now available as an inexpensive generic.

For this study, Mazzone and his colleagues reviewed and compared electronic medical records on 225 diabetics with lung cancer with a similar number of diabetic patients who did not have lung cancer, although both groups shared other risk factors such as age, smoking history and gender.

"Forty-one percent of those with lung cancer had taken one of these medications at some point prior to developing the cancer, and 96 percent of all the controls had taken one of these medications in diabetic treatment," reported Mazzone, director of the lung cancer program at The Respiratory Institute at the Cleveland Clinic in Ohio.

Of those with lung cancer, 25 percent of those who developed metastatic disease (which is disease that has spread) were taking one of the medications versus 48 percent of those who did not take one of the drugs.

Also, "the longer someone took the medication, the more protective it seemed to have been," Mazzone said. "This also supports the premise that these medications might be able to serve as risk modifiers."

But there's a long way to go before doctors can start recommending metformin, Avandia or Actos for otherwise healthy people to protect against lung cancer.

"There have been no direct studies using these medications in humans for the purpose of preventing or altering the course of lung cancer," Mazzone said. "We need to fully understand the mechanisms by which these medications might prevent or change the course of cancer. We need to develop large clinical trials using these medications and following people forward to see if they are protective, as retrospective studies have suggested."

And the safety profile of these drugs or similar compounds need to be investigated if the drugs are going to be used in non-diabetics, he said. For instance, both Avandia and Actos have been shown to raise the chances of developing certain cardiovascular risk factors.

"This is the sort of study that raises an interesting question that maybe there is some activity," added Dr. Lucas Wong, an associate professor of internal medicine at Texas A&M Health Science Center College of Medicine, co-director of the Gastrointestinal Cancer Program and principal investigator of the Community Clinical Oncology Program at Scott & White in Temple, Texas. "The harder thing is to figure out how to dose the medication, how to use, [but] just because you're a diabetic and you're taking this medication doesn't mean you're not going to get lung cancer."

It should be noted that research presented at meetings is not subject to the same scrutiny as peer-reviewed research published in respected journals.

More information

The U.S. National Library of Medicine has more on thiazolidinediones.