Although smoking is the No. 1 cause of lung cancer, viruses may also contribute to the development of this fatal disease, new research suggests.

Dr. Arash Rezazadeh and colleagues from the University of Louisville, Kentucky presented their findings at the 1st European Lung Cancer Conference, jointly organized by the European Society for Medical Oncology (ESMO) and the International Association for the Study of Lung Cancer (IASLC) in Geneva.

For the study, the researchers examined lung cancer tissue samples taken from 23 patients, all smokers. Six samples tested positive for HPV, although one case resulted from cervical cancer that spread to the lungs. The remaining five HPV-positive samples comprised the following stains: HPV-16, HPV-11, and HPV-22.

“The fact that five out of 22 non-small-cell lung cancer samples were HPV-positive supports the assumption that HPV contributes to the development of non-small-cell lung cancer (NSCLC),” the study authors say in a news release, Webmd.com reports.

“We think HPV has a role as a co-carcinogen which increases the risk of cancer in a smoking population,” Dr. Rezazade said.

He added that more study needs to be done in the near future. “In terms of HPV, our finding is pretty controversial. And this is just the beginning of the road. There is much more work to be done. But it's important to know that being infected with this virus does appear to increase lung cancer risk.”

However controversial or not the findings of the study are, they raise an intriguing question: Could an HPV vaccine similar to Gardasil, the one approved to protect women against cervical cancer, also help thwart lung cancers? - See Viruses May Increase Lung Cancer Risk