India has been facing a significant rise in cases of non-smoker lung cancer in recent years, making it a major concern for public health officials and researchers. This trend has led to India becoming the centrestage of maximum cases of non-smoker lung cancer worldwide.
Non-smoker Lung Cancer
Source:News-Medical
Lung cancer occurs when abnormal cells in the tissue of one or both lungs grow in an uncontrolled manner. There are two main types of lung cancer: Small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). NSCLC accounts for approximately 87.3 per cent of all lung cancer cases locally and is further classified into subtypes based on cell type and mutations.
A Study on the Issue
Published in The Lancet’s e-Clinical Medicine Journal, the study reveals that lung cancer in India appears around a decade earlier than in Western countries. This cancer is typically diagnosed between ages 54 and 70.This is probably due to India’s younger population i.e., median age of 28.2 years compared to the USA (38 years) and China (39 years). Meanwhile, the incidence rate of lung cancer has increased from 6.62 per 1,00,000 in 1990 to 7.7 per 1,00,000 in 2019, with significant rises expected in urban areas by 2025.The gender ratio of lung cancer cases shows higher tobacco use among men (42.4% vs. 14.2%) among women.
There are several reasons why this phenomenon is occurring in India, and it is important to understand the contributing factors in order to address this growing issue effectively.
Lung Cancer in Non-smokers
Source:Drug Target Review
One of the primary reasons for the high prevalence of non-smoker lung cancer in India is the widespread exposure to indoor air pollution. Indoor air pollution is a major risk factor for lung cancer, with studies showing that the levels of pollutants such as particulate matter, carbon monoxide, and nitrogen dioxide can be significantly higher indoors than outdoors in many Indian households. This is primarily due to the use of solid fuels for cooking and heating, such as wood, coal, and dung, which release harmful pollutants when burned. As a result, individuals who are not exposed to tobacco smoke are still at risk of developing lung cancer due to prolonged exposure to indoor air pollution.
Tuberculosis
Another contributing factor to the high rates of non-smoker lung cancer in India is the country’s high prevalence of tuberculosis (TB). TB is a major risk factor for lung cancer, and India has one of the highest rates of TB in the world. Studies have shown that individuals who have had TB are at an increased risk of developing lung cancer, even if they have never smoked. The presence of TB in the lungs can lead to chronic inflammation and scarring, which can increase the likelihood of developing cancerous cells in the affected tissues. Therefore, the high burden of TB in India is likely contributing to the rising rates of non-smoker lung cancer in the country.
Environment
Additionally, environmental factors such as outdoor air pollution and occupational exposures are also playing a role in the increasing cases of non-smoker lung cancer in India. Outdoor air pollution, primarily caused by vehicular emissions, industrial activities, and construction dust, has been linked to an increased risk of lung cancer in non-smokers.
India’s rapidly growing urbanization and industrialization have led to deteriorating air quality in many cities, exposing residents to higher levels of pollutants that can damage the lungs and increase the risk of developing cancer.
Similarly, workers in industries such as mining, construction, and manufacturing are often exposed to carcinogenic substances that can cause lung cancer, even in the absence of smoking.
Genetics
Furthermore, genetic factors may also contribute to the higher rates of non-smoker lung cancer in India. Certain genetic mutations and variations have been associated with an increased risk of developing lung cancer, particularly in individuals who do not smoke. Studies have shown that these genetic factors may be more prevalent in certain populations, including those of South Asian descent, which could partly explain why India has become the centrestage of maximum cases of non-smoker lung cancer.
A genomic analysis of lung cancer in non-smokers conducted by the US National Institutes of Health (NIH) has revealed for the first time three molecular subtypes of lung cancer in people who have never smoked. These insights could help unlock the mystery of how lung cancer arises in people who have no history of smoking and may guide the development of more precise clinical treatments.
The genomic analyses also revealed three novel subtypes of lung cancer in never-smokers, to which the researchers assigned musical names based on the level of “noise” in the tumours. The predominant “piano” subtype had the fewest mutations: it appeared to be associated with the activation of progenitor cells, which are involved in the creation of new cells. This subtype of tumour grows extremely slowly, over many years and is difficult to treat because it can have many different driver mutations. The “mezzo-forte” subtype had specific chromosomal changes as well as mutations in the growth factor receptor gene EGFR, which is commonly altered in lung cancer and exhibited faster tumour growth. The “forte” subtype exhibited whole genome doubling, a genomic change that is often seen in lung cancers in smokers.
Limitations of Genetic Study
The study was limited to people who had never smoked, so the researchers did not find any mutational signatures that have previously been associated with direct exposure to tobacco smoking. They also did not find those signatures among the 62 patients who had been exposed to second-hand tobacco smoke. However, Landi cautioned that the sample size was small and the level of exposure highly variable.
According to the team, a future direction of this research will be to study people of different ethnic backgrounds and geographic locations and whose exposure history to lung cancer risk factors is well described.
The study was published in Nature Genetics.
Conclusion
In conclusion, the rising rates of non-smoker lung cancer in India can be attributed to a combination of factors, including exposure to indoor air pollution, high prevalence of TB, environmental and occupational exposures, and genetic predisposition.
Addressing this growing issue will require a comprehensive approach that focuses on reducing indoor air pollution, improving TB control measures, minimizing exposure to outdoor air pollution and occupational hazards, and conducting further research to better understand the genetic factors involved. By addressing these factors and implementing effective prevention and screening programs, we can work towards reducing the burden of non-smoker lung cancer in India and improving the overall health outcomes for the population.
2.https://www.channelnewsasia.com/advertorial/lung-cancer-unmasked-not-just-smokers-disease-4421321
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