New model estimates smoking's legal attribution to lung cancer cases

(Medical Xpress)—A newly developed model estimates smoking's attribution to lung cancer and finds that more than 90 percent of Quebec lung cancer cases can be legally attributed to smoking, according to a new study in the American Journal of Public Health published by Jack Siemiatycki of the University of Montreal's Institute for Public Health Research. Legal attribution incorporates the notion of "more likely than not" or equivalently that the probability of causation due to smoking was greater than 0.50.

The model is based on the dose-response relationship between smoking and lung cancer, and the smoking pattern among lung cancer patients. Researchers measured the extent of smoking through a pack-years measure, which integrates the amount smoked per day and the number of years that the person smoked. The model was developed in response to a request from lawyers of a class action suit in Quebec against the tobacco industry on behalf of patients with lung cancer that was allegedly caused by smoking.

The researchers estimated that the amount of smoking required to satisfy the legal criterion of "more likely than not" is between 3 and 12 pack-years, depending on the modelling assumptions. Based on smoking patterns among lung cancer cases in Quebec, they further estimated that more than 90 percent of the cases satisfied even the most conservative of these thresholds and could be legally attributed to smoking.

"In Quebec, where there were about 6,200 newly diagnosed cases of lung cancer per year from 1995 to 2006, this translates to a total of about 5,700 cases per year that would satisfy the criterion of probability of causation greater than 0.50," the researchers explain.