Risk of Lung cancer among passive smokers

Contributed by Dr. Manish Chomal, Head-Radiation Oncology, HCG Hospitals Jaipur

Cancer is a deadly disease and lung cancer is one of the most common causes of cancer-related deaths worldwide. Approximately 11-12% of all cancer cases worldwide are lung cancers. In India, about 70,000 new lung cases are diagnosed every year which comprises approx. 6-7% of all cancer cases. Tobacco consumption is a significant risk factor for lung cancer. Smoking has been predominant in rural parts of India and with an increase in stress, social participation, it has become a trend amongst Indian youth.

It is well known that smoking is the most important factor in increasing the lifetime risk of lung cancer. With increasing awareness about the ill-effects of smoking & its association with cancer, in the western world smoking habit is gradually coming down with some decline in lung cancer incidences. However, at the same time, there is a rise in lung cancer among non-smokers. Awareness in society regarding the ill effects of secondhand or passive smoking is lacking. Sensitization of masses for passive smoking as a major risk factor for lung cancer is the need of the hour.

Around 15–20% of men and over 50 % of women with lung cancer are non-smokers. The primary causes of cancer in non-smokers are passive/second-hand smoking, environmental exposures to asbestos, chromium, arsenic & pollutants. Multiple studies have suggested that 15–35 % of lung cancer in non-smokers is due to second-hand smoke exposure. The indirect exposure to tobacco smoke predisposes the other family members to an increased risk of cancers including lung cancer. The risk increases with age.  Children get asthma & other breathing disorder in childhood, but with long time exposure to passive smoking, the risk of acquiring lung cancer at a later age also increases among them.

Lung cancer in non-smokers also has some genetic predispositions. There are specific germline mutations that have been identified in families with high rates of lung cancer in non-smokers. In general, there is approx.  25% increased risk of any cancer among first-degree relatives. Some receptor mutations (EGFR) are found associated with this cancer. The identification of this mutation has led to the development of targeted treatment for individuals with this mutation.

The signs & symptoms of lung cancer in smokers as well as non-smokers are similar. Symptoms of lung cancer are often nonspecific and include symptoms like cough, dyspnea, weight loss, and loss of appetite. More specific symptoms do include chest pain and blood in cough/sputum which can be seen in other diseases as well.

Non-smokers with lung cancer respond to standard treatment similar to smokers, they do not have a better prognosis.  Mortality rates are not different from the smoker group, as it largely varies with the stage of cancer. There are many genetic mutations associated with non-smoker adenocarcinoma lung which can be targeted with novel treatment approaches called targeted therapies or immunotherapies. Studies involving these medications have suggested improved response rates and survival in non-smokers over smokers.

There are no screening recommendations for lung cancer in non-smokers, but it is advised to consult your doctor/oncologist if there is a family history of lung cancer or any of the symptoms are persisting.  Early diagnosis is shown to improve outcomes & better chances of cure. The treatment includes surgery or radiotherapy in early stages, radiotherapy, and or chemotherapy in advanced stages. Now there are precise radiotherapy techniques which are capable of focused targeting of cancer lesion with minimal side effects. Likewise, newer systemic therapies like targeted & immunotherapies offer better outcomes & with fewer side effects. It is critical to take more precautions for respiratory health in order to save lives and hence people should quit smoking and avoid second-hand smoke.

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