Worldwide, as per the Global Cancer Observatory, in 2020, lung cancer will stand in the 2nd position as the most diagnosed form of cancer, with 2,206,771 new cases annually, but the mortality is high as it takes the 1st position in terms of mortality, causing 1,796,144 deaths. Lung cancer is the 3rd most commonly diagnosed cancer among Southeast Asians (185,636 new cases; 7.8%) and is the leading cause of death when compared with other cancers, causing 166,260 (10.9%) deaths. Annually, 72,510 cases (5.8%) and 66,279 deaths (7.8%) of lung cancer are reported in India.
According to the article published in the Lancet journal, the eligibility criteria for this study were cases of thoroughly examined lung cancers. India accounted for 9 of these studies.
Epidemiology and Risk Factors
Lung cancer affects Indians 10 years earlier than Western people, with a mean age of 54–70 years, which might be because the average median age of Indians is 28.2 years. In contrast, the median age is 38 and 39 years in the USA and China, respectively. Other risk factors that might be responsible for lung cancer in non-smokers are air pollution and germline mutations. There was an increase in lung cancer age-standardized incidence rates (ASIR) from 10.36 to 11.16 in men and 2.68 to 4.49 in women. The etiological causes could be tobacco smoking and indoor and outdoor pollution with particulate matter of ≤2.5 µm. By 2025, the cases would rise to 81,219 in men and 30,109 in women.
According to some studies, around 40–50% of the Indians who have lung cancer are never smokers. The major risk factors for lung cancer in non-smokers are air pollution (especially particulate matter of 2.5 µm), which is usually seen in urban areas; occupational exposure to asbestos from various industries; and exposure to agents like chromium, cadmium, arsenic, and coal products at the workplace. In rural areas, the major risk factor would be smoke at home due to biomass fuel. Other factors might be a previous history of lung disease, genetic factors, and hormonal status, which increase the incidence of lung cancer.
The estimated age-standardized 5-year survival for lung cancer was low in India at 3.7% as compared to the USA (21.2%) and Japan (32.9%).
Tobacco Consumption
Southeast Asian countries are the largest consumers and producers of tobacco in the world. Among them, India is in 3rd position in production and 2nd in consumption. Currently, 42% of men and 14.2% of women smoke tobacco. The mean age is 18.7 years for starting daily tobacco use. Every 3 in 10 people are exposed to second-hand smoke. Tobacco users had an increased risk of 5.2 times for developing small cell lung cancer and oat cell carcinoma, 3.9 times for developing adenocarcinoma, and a 26.2 times increased risk of developing squamous cell carcinoma.
The risk factors that might contribute to lung cancer among tobacco consumers are:
Dosage and duration of tobacco smoking: the risk of developing lung cancer increased with the number of products smoked per day and the years of continuing smoking.
Type of tobacco product used
Tobacco cessation: the risk of lung cancer decreases in people who reduce their smoking or completely quit smoking.
The World Health Organization (WHO) MPOWER programme (a set of six measures designed to lower the demand for tobacco) and ratification of the Framework Convention on Tobacco Control (FCTC) were implemented by Southeast Asian countries.
According to the Global Adult Tobacco Survey (GATS) and the Global Youth Tobacco Survey (GYTS), 22% of the world’s adult smokers (≥15 years) and 34% of children (13–15 years) who use tobacco reside in Southeast Asia. Tobacco use has decreased from 47% in 2000 to 29% in 2018 and is expected to decline further to 25% by 2025. On February 2, 2019, a telephonic service named “Tobacco Quit Line” was established in India.
Tuberculosis and Lung Cancer
TB and lung cancer are usually present concurrently. 0.9% of patients with lung cancer had pleuropulmonary TB, according to the data reported from the Postgraduate Institute of Medical Education and Research in Chandigarh, India. According to a report by Ramachandran et al., before the correct diagnosis was made, 29% of patients with lung cancer had been misdiagnosed as TB, and 27.1% were treated with antituberculous therapy (ATT). According to Indian studies, the misdiagnosis rate is 17–22%.
Histopathology
According to a 10-year analysis, it was reported that the most common pathological type was adenocarcinoma (34%), followed by squamous cell carcinoma (28.6%) and small cell lung cancer (16.1%).
Biology
The diversity of the Indian people determines the genetic makeup of lung cancer. The prevalence of EGFR mutations and ALK rearrangements was reported to be 30% and 10%, respectively.
EGFR mutations
The EGFR mutation rate is 23–30% among Indians, 10–15% among Americans/Europeans, and 27–62% among East Asians. The differences are due to genetic influences. EGFR mutation frequency was directly linked to smoking history in pack years and ethnicity, according to a PIONEER study conducted. The highest EGFR mutation rate was found in the people of Kinh at 64.2%, and the lowest was among Indians at 21.9%.
KRAS mutations
The KRAS mutation rate among Americans/Europeans was 25–50% and 5–15% among East Asians. A 30.6% alteration rate in the KRAS gene was seen in a recent study from the Rajiv Gandhi Cancer Institute, a tertiary care hospital in Delhi, India.
Reference:
1. https://www.thelancet.com/journals/lansea/article/PIIS2772-3682(24)00080-5/fulltext#secsectitle0025
By Dr. Siddiqua Parveen
