FRIDAY, Dec. 2 (HealthDay News) -- Opera legend Beverly Sills never smoked. Neither did actress and health advocate Dana Reeve, wife of the late actor Christopher Reeve.

And yet in 2007 and 2006, respectively, both joined the ranks of about 32,000 Americans each year who never touch a cigarette but die of lung cancer anyway.

In fact, experts say, one in every five cases of the leading cancer killer occurs in nonsmokers. The annual death toll among this group now approaches that of breast cancer (about 40,000 per year) and is roughly equal to that of prostate cancer (32,000). Many never-smoking women may also be unaware that they are more than twice as likely to die of lung cancer as they are of ovarian cancer (14,000 deaths per year).

Numbers like those have experts calling for a shift in the public's thinking on lung cancer, away from its label of "the smoker's disease."

"We say, 'If you have a lung, you can get lung cancer,'" said Linda Wenger, executive director of Uniting Against Lung Cancer (UALC), a nonprofit advocacy group aimed at reaching a better understanding of lung cancer. The group was founded after the death in 2001 of Joan Scarangello, an ABC and NBC journalist and lifelong nonsmoker who fell victim at age 47 to lung cancer.

"She was very healthy, she was a runner," Wenger said, but the disease claimed Scarangello as it has many never-smokers. "We need to look at lung cancer as being a cancer like any other," Wenger added.

Many experts believe that the stigma around smoking that accompanies lung cancer -- that its victims somehow "brought it on themselves" -- has dampened public sympathy for patients and hindered funding for research.

"The lung cancer research field is definitely the stepchild in the [cancer research] family, and we're sure a lot of that has to do with stigma," said Holli Kawadler, UALC's scientific program director. She noted that, in terms of funding received from the U.S. National Cancer Institute, "the numbers are $27,000 in research per cancer death for breast cancer, compared to only about $1,400 per cancer death for lung cancer."

"It's very disheartening for the whole field," Wenger said. "We have a partner out there, his wife has lung cancer but she never smoked. And she has the attitude that 'I never smoked, but cigarettes are going to kill me' because the money is not there for research, because of the smoking stigma."

Lung cancer's lethal nature may also be hindering efforts to boost awareness and funding for research, experts add.

"Unlike other cancers where there is better funding, lung cancer patients aren't well enough to really advocate for themselves," explained Dr. James Dougherty, medical and scientific advisor for the Lung Cancer Research Foundation (LCRF), based in New York City. "When they get the diagnosis they often get sick pretty quickly, so they aren't about to publicly take on the role of saying 'Look, I have a problem, I need help.'"

Still, even with limited funding, scientists are slowly uncovering clues to the origins and distinct nature of lung cancer in never-smokers. One obvious starting point is the fact that women are affected far more often than men.

"Among never-smokers with lung cancer, women outnumber men two-to-one," Wenger said.

According to experts at the LCRF, the reasons for the disparity aren't clear, but early research is suggesting that, much like breast tumors, lung tumor aggressiveness in women appears linked to estrogen. Other factors, as yet unknown, may also be at play.

"We're also learning much more about the differences in the biology of [lung cancer in] smokers and nonsmokers," Dougherty added. He pointed to LCRF-funded research under way at M.D. Anderson Cancer Center in Houston, "specifically looking at some new potential markers on the [tumor] cells of people who have never smoked. Hopefully that will lead to the identification of better treatment options for nonsmokers."

Determining risk factors that might place certain never-smokers at especially high risk for lung cancer is another focus of research. The dream, experts said, is to somehow devise an accurate "panel" of biological and other factors that could serve as a basis in pinpointing at-risk individuals who may need closer monitoring.

All of these research advances will depend on much better funding, however. In the meantime, the stigma of smoking that overshadows never-smokers newly diagnosed with lung cancer continues.

"We hear a lot from people that the first thing they are asked after diagnosis is, 'Did you smoke?'" said Kawadler. "That's very tough."

More information

Find out more about ongoing efforts to fight lung cancer at the Lung Cancer Research Foundation.