A newly developed model legally attributes more than 90% of lung cancer cases in Quebec to smoking, based on a dose-response relationship between smoking and lung cancer, as well as the smoking pattern among lung cancer patients.

The study, led Jack Siemiatycki and his team from the University of Montreal, was published in this month’s American Journal of Public Health, and began as a response to a request from lawyers for a class action suit launched in Quebec on behalf of all patients suffering from lung cancer caused by cigarette smoking.

In this novel approach, the team attempted to estimate what proportion of lung cancers in Quebec could be included in the “more likely than not” criterion, which is synonym of a greater than 0.50 probability of lung cancer being caused by smoking.

The extent of smoking was evaluated as the amount an individual smoked per day and the total number of years smoking, resulting in a 3 and 11 pack-years estimative to fulfill the “more likely than not” criterion, depending on the modeling assumptions.

With 90% of cases studied satisfying such thresholds, the researchers explained that this translates into a total of about 5,700 cases per year in Quebec.

The developed methodology improves the ability to conduct class action suits against the tobacco industry.