For years, researchers have attempted to understand the rising rates of lung cancer among women. While the fact that more women smoke today than did forty years ago is an indisputable contributor, some experts make the case that women are biologically more vulnerable to the disease than men.

“The question of whether or not women are more susceptible to lung cancer remains controversial. Some studies suggest that women who smoke are more apt to develop lung cancer at an earlier age than men, suggesting greater susceptibility, but other studies refute this. Biologically, several researchers are trying to determine whether or not estrogen or other hormones influence susceptibility to tobacco carcinogens, but there is again no definitive evidence of a link,” explains Dr. Gregory P. Kalemkerian, professor of Medicine and co-director Thoracic Oncology at the University of Michigan Medical Center in Ann Arbor, Michigan.

A team of Harvard University researchers attempted to get to the bottom of the biology question by comparing prospective studies, which assess smoking habits of a population, to incidence rates of lung cancer in women and men, making sure to account for complicating factors like number of cigarettes smoked per day and age at start of smoking. Their conclusion—risk of developing lung cancer is determined mainly by the quantity, duration and intensity of an individual’s smoking history. This conclusion was not without a complicating factor when it comes to biology, however.

“In this direct comparison of incidence rates, we found no difference in lung cancer incidence in male and female current smokers, but there was a possibility of a higher incidence of lung cancer in female past smokers than in male past smokers (on the order of 30 per cent higher). I do not have an explanation for this. However, when we examined specific histologic types of lung cancer, we found that women were at higher risk of adenocarcinoma than men. Adenocarcinoma is thought to be less associated with smoking than the other types of lung cancer, so it is possible that there are factors other than smoking that make women more susceptible to lung cancer than men,” says Dr. Diane Feskanich, co-author of the study and instructor in Medicine at Harvard Medical School and associate epidemiologist, Department of Medicine Brigham and Women's Hospital.

Debate continues as to why rates have risen among women, but everyone agrees that cigarette smoking not biology is the real villain when it comes to affecting lung cancer statistics.

“The main causes of lung cancer are: one, smoking, two, smoking, three smoking, four, smoking—you get the idea,” says Dr. Kalemkerian.

“Ninety percent of people with lung cancer are smokers or former smokers. That still leaves about 10 per cent who are non-smokers (about 15,000-20,000 people per year in the U.S.). Second-hand smoke is a cause, but is much less of a risk than active smoking. Other potential causes are: radon (a naturally occurring radioactive gas), asbestos, polycyclic aromatic hydrocarbons, and some chronic lung diseases, but the risks from these are dwarfed by smoking,” he concludes.

So how do we decrease our chance of developing lung cancer?

“There is only one piece of advice, and that is don't smoke and don't hang around smokers. If we had such solid advice to offer for other types of cancer, we would be very happy,” advises Dr. Feskanich.