Commonly associated factors are: Outdoor air pollutionsecondhand smoke, domestic fuel smoke (wood burning), chronic lung diseases, occupational exposure to carcinogenic chemicals (silica, arsenic, chromium, cadmium, nickel), ionizing radiation (such as radon), family history and genetic causes .
Secondhand smoke: Secondhand smoke is a major risk factor for lung cancer among those who have never smoked. An American multicenter study found a 30% increased risk of lung cancer in people who never smoked and who had a smoking spouse. Importantly, there is also an increased risk for non-smokers who have a spouse who is a smoker. In a meta-analysis that included 55 studies, women married to a smoker were found to have a 27% increased risk of lung cancer.
Air pollution – Outdoor air pollution is a mixture of various pollutants from natural and anthropogenic sources, such as transportation, industrial activity, energy generation, among others. Outdoor air pollution and particles from outdoor air pollution are carcinogenic to humans
Radon: Radon is a radioactive gas produced by the decay of uranium present in soil and rocks. The International Agency for Research on Cancer (IARC) defined it as a human carcinogen in 1988 and epidemiological studies have successfully correlated radon exposure with lung cancer in both mine workers and other environmentally exposed populations. It is considered the second most important risk factor for the development of lung cancer after tobacco and probably the main risk factor among those who have never smoked.
Occupational exposure to carcinogenic chemicals or ionizing radiation: Occupational exposure to different types of carcinogenic chemicals or ionizing radiation is thought to be associated with 5% to 10% of lung cancer cases, and exposure to asbestos It is currently the most important factor, with a proportion five times greater. increased risk of lung cancer.
Family history/genetic causes: More recently, studies have also investigated the possibility of an inherited predisposition to lung cancer, and it is estimated that 5 to 10% of lung cancer patients have germline mutations in hereditary cancer genes. Family aggregation studies have estimated an increased risk of developing lung cancer of up to 4-fold based on family history of lung cancer in first-degree relatives and respective age at diagnosis.
Lung disease: Another important risk factor for developing lung cancer in non-smokers is underlying lung disease.
Environmental exposures: Several studies have also linked environmental exposures to lung cancer; Some known exposures include asbestos, chromium, and arsenic. Chronic exposure to cooking fumes from wood burning or frying has been linked to a higher rate of lung cancer in non-smokers. This problem is more evident in developing countries where women are primarily in charge of kitchen duties and can spend hours each day cooking over open flames. This exposure is believed to be the cause of some of the disproportionate rates of lung cancer within this population.
There is no recommended screening test for lung cancer in non-smoking men and women. Lung cancer symptoms should not be overlooked in women and non-smokers. The treatment of lung cancer in non-smokers is similar to that of smokers but the prognosis is better. Most of them harbor mutations that are treated with newer therapies and targeted agents. Regardless of whether they smoke, women with lung cancer tend to outlive men with lung cancer.
(Dr G. Vamshi Krishna Reddy, Director of Oncology Services, Consultant Medical Oncologist and Hemato-Oncologist, Yashoda Hospitals, Hyderabad)