Possible Viral Links to Lung Cancer Risk Uncovered
FRIDAY April 25, 2008 -- Although smoking is well-established as an independent risk factor for lung cancer, two new studies suggest that two different viral infections might boost a smoker's already substantial risk for developing the disease.
While the specific viruses at issue -- human papillomavirus (HPV) and measles -- may not directly cause lung cancer, they seem to aggravate the negative impact of tobacco, American and Israeli researchers say.
Both findings were presented Friday by separate research teams attending the European Lung Cancer Conference in Geneva.
"In terms of HPV, our finding is pretty controversial," said study author Dr. Arash Rezazadeh, a fellow of medical oncology and hematology at the University of Louisville in Kentucky. "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."
As for the role of measles, the second study's lead author, Dr. Samuel Ariad, from the department of oncology at Soroka Medical Center in Beer Sheva, Israel, said that infection -- perhaps even asymptomatic infection -- seems to be associated with half of the lung cancer cases he tracked.
"Measles virus by itself is unlikely to be carcinogenic," he said. "[But] it probably modifies previous damage to DNA caused by smoking."
Both studies specifically focused on the viral impact on non-small cell lung cancer (NSCLC) risk. According to the American Cancer Society, 85 percent to 90 percent of all lung cancers are of this variety. Estimates regarding all forms of lung cancer indicate that 215,000 new cases will be diagnosed in the United States this year alone.
In the HPV study, Rezazadeh and his colleagues analyzed lung tissue samples taken from 23 lung cancer patients being treated in Kentucky. Kentucky, they noted, is the state with the highest rate of adult and teenage smoking in the United States, as well as the highest rate of NSCLC.
Among the patients -- all of whom were smokers -- five were found positive for infection with a variety of HPV strains.
The authors said this frequency of infection "supports the assumption that HPV contributes to the development of NSCLC." They point out that HPV is already known to be the cause of all cases of cervical cancer, a vaccine for which has recently become available. It has also recently been implicated as a possible cause for head and neck cancer.
Further studies are planned to look for signs of HPV infection in the respiratory tract of lung cancer patients and to explore the possibility for using HPV infection as a screening indicator for the disease.
In the measles study, Ariad and his team analyzed lung tissue samples taken from 65 Israeli lung cancer patients between the ages of 40 and 84. Ninety percent were smokers, and most were in the early stages of the disease.
The authors found evidence of measles infection in 54 percent of the patients. The likelihood of viral infection, they observed, went up with age.
They concluded that "a possible association" exists between measles and NSCLC.
Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, described both research efforts as "interesting." But he cautioned that more research needs to be done on each front.
"The question I have for the measles association has to do with vaccination, since in the U.S., at least, we have near universal coverage," he noted. "So although the measles vaccine may lose some of its effectiveness over time, it would be interesting to know if this finding would apply to a country such as ours where most people are vaccinated."
"But I think the HPV study is the more interesting of the two," Lichtenfeld added, "since HPV is obviously already implicated in other cancers. But this is a small study, and it only suggests a possible link to lung cancer without answering a lot of questions. I would like to know, for example, whether patients who are not smokers but who develop lung cancer have a higher rate of HPV. But for now, I would not yet conclude that HPV increases risk, nor would I tie the HPV vaccine to any risk."
For more about lung cancer, visit the American Cancer Society.
Posted: April 2008