Study Analyzes Incidence, Death Rate for Non-Smoker Lung Cancer
Lung cancer tops the list both for new cancer diagnoses and cancer deaths here in the US. While smoking is to blame for the overwhelming majority of lung cancers, a significant proportion of lung cancer cases (10% to 15%) are caused by factors other than smoking. The death of lifelong non-smoker Dana Reeve (wife of actor Christopher Reeve) of lung cancer at the age of 44 in 2006 raised public awareness — and worry — that avoiding smoking may not fully protect non-smokers from lung cancer.
Though the media has paid a lot of attention to lung cancer in non-smokers, many questions remain unanswered and misinformation abounds about the disease, according to Michael J. Thun, MD, at the American Cancer Society. He and a team of researchers set out to learn what they could by combining data on the incidence and mortality rates of almost two million self-reported “never-smokers” with lung cancer, from studies based in North America, Europe and Asia over a 70-year period.
The study measured how frequently lung cancer occurs in or kills lifelong non-smokers — it did not examine why. As such, the analysis did not examine second-hand smoke and other known risk factors of lung cancer, such as radon, asbestos and indoor air pollution. While it is “well established that second-hand smoke increases the risk for lung cancer, we were unable to evaluate it and other risk factors because this data was not available in many of the cohorts (groups) that were studied,” explained Dr. Thun.
Here’s what they learned…
- Overall incidence of lung cancer among lifelong non-smokers is rare (fewer than 40,000 cases per year), similar to the incidence rate for brain cancer and other nervous system cancers.
- The risk that a never-smoker will die from lung cancer before age 85 is slightly higher for men (1.1%) than women (0.8%), but quite small for both genders.
- Overall, incidence and death rates for lung cancer among non-smokers have remained stable over the time period studied.
The findings contradict two long-held assumptions — that non-smoking women have a higher risk of dying from the disease than non-smoking men, and that lung cancer among non-smokers has been increasing over the decades. The study was published in the September 2008 issue of PLoS Medicine, a peer-reviewed journal published by the Public Library of Science.
Non-smoking Asians living in Asia (not in the United States) and African Americans have higher rates of lung cancer and are more likely to die of the disease compared with non-smokers of European descent. The higher lung cancer risk among Asian women compared with Western women was seen to occur over a wide area that included China, Japan, the Philippines and Singapore. Dr. Thun speculates that one cause may be their tradition of cooking with open woks, which is known to produce carcinogens dispersed through fumes resulting from heating cooking oil at high temperatures.
Clearly there is a need for more information and research about non-smoking-related lung cancer. Dr. Thun acknowledges that this analysis represents an early step. We’ll keep you posted as more findings emerge.