Epidemiology of Lung Cancer

Aarthi Iyer, Abhishek Shankar

Department of Radiation Oncology, Dr BR Ambedkar Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India

Lung cancer is the most commonly diagnosed cancer type in the world with 2.094 million (11.6%) new cases of all diagnosed cancer cases with high mortality accounting for 1.8 million deaths (18.4%) in 2018. A total of 1,368,524 and 725,352 new lung cancer cases were reported in men and women respectively. The trend of lung cancer has changed over the decades but it is still a leading cause of death among men (1, 2).

The incidence of lung cancer has significantly increased in the last three decades and has a worrisome increase in developing countries. The burden of lung cancer is very high in Asia with an estimated incidence of over 1.2 million cases and approximately 1.07 million deaths. Lung cancer incidence is at the top of the list among males, but it ranks third in women after breast and cervical cancers in Asia (1).

The highest incidence rate of lung cancer was reported in South Korea China, Turkey, Singapore, Philippines (2). An estimated 774,323 new cases were reported in China with a mortality of 690,567 people (1). China accounts for almost half of the total cases of lung cancer worldwide. Furthermore, the incidence of lung cancer in China is increasing, with a greater number of young lung cancer patients (3). In India, lung cancer ranks fourth (5.9%) in overall cancer incidence and second among males, while it ranks third in mortality (8.82%) due to cancer after breast cancer and head & neck cancer (1).

According to the Population Based Cancer Registries Report 2016, the incidence of lung cancer is higher in the North-Eastern Region of India where incidence varies from 3.22–to 28.25 cases, followed by the southern region, eastern region, and northern regions. Incidence is low in the western and central regions as compared to other regions in India. Despite variation in incidence geographically, lung cancer is the leading cancer in many cancer registries in India (4,5), also the cases of non-smoking lung cancer in India are on the rise.

There are several risk factors for the development of lung cancer. CDC states cigarette smoking is the number one risk factor for lung cancer. In the United States, cigarette smoking is linked to about 80% to 90% of lung cancer deaths. Using other tobacco products such as cigars or pipes also increases the risk of lung cancer. Smoke from other people’s cigarettes, pipes, or cigars (second-hand smoke) also causes lung cancer. In the United States, one out of four people who do not smoke, including 14 million children, were exposed to second-hand smoke from 2013 to 2014. After smoking, radon is the second leading cause of lung cancer.

Smoking, a major risk factor for lung cancer, accounts for about 85% of all lung cancers in current or former smokers. In recent times, lung cancer cases among non-smoker females is becoming an important concern in developing countries . Since most lung cancers are diagnosed at a later stage lung cancer survival remains poor, not exceeding 15% at 5 years. Routine lung cancer screening is currently not recommended. Several studies have reported detection of lung cancer at an early stage with improved survival by making use of low-dose Computer Tomography in lung cancer screening. However, the epidemiology of lung cancer may be different in developing countries (11).
While the prevalence of smoking, air pollution, and environmental hazards are considered to be significantly higher in developing countries, up to 30–40% of Asian lung cancer patients had never been smokers, in contrast to only 10% of patients in the United States

The U.S. Environmental Protection Agency (EPA) estimates that radon causes about 21,000 lung cancer deaths each year. The risk of lung cancer from radon exposure is higher for people who smoke than for people who don’t smoke. However, the EPA estimates that more than 10% of radon-related lung cancer deaths occur among people who have never smoked cigarettes. Other substances found at some workplaces that increase risk include asbestos, arsenic, diesel exhaust, and some forms of silica and chromium.

Genetic predisposition to lung cancer is also one of the risk factors including familial lung cancer with germline mutation, there is also a risk in cancer survivors who had radiation therapy to the chest, particularly people who have been treated for Hodgkin disease or women who get chest radiation after a mastectomy for breast cancer.
Lung cancer screening is largely restricted to developed countries despite the high prevalence of lung cancer cases even in developing countries. It is showing a rising trend because of tobacco use, environmental pollution along with various other factors. There are frameworks for cancer screening in many developing countries but lung cancer screening is not included despite the high incidence of lung cancer. This may be attributed to a lack of infrastructure, no willingness for screening among high-risk populations, fear of disease, overdiagnosis, continuum of care for treatment, and psychological impact .

1. GLOBOCAN 2018. International Agency for Research in Cancer 2018. Available online: https://gco.iarc.fr/
2. Parkin DM, Bray F, Ferlay J, et al. Global cancer statistics, 2002. CA Cancer J Clin 2005; 55:74-108.
3. Chen W, Zheng R, Baade PD, et al. Cancer statistics in China, 2015. CA Cancer J Clin 2016; 66:115-32.
4. Asthana S, Patil RS, Labani S. Tobacco-related cancers in India: A review of incidence reported from population-based cancer registries. Indian J Med Paediatr Oncol 2016; 37:152-7.
5. Mohan S, Asthana S, Labani S, et al. Cancer trends in India: A review of population-based cancer registries (2005-2014). Indian J Public Health 2018; 62:221-3.