In this study, we performed the updated epidemiology of lung cancer burden in 2020 and analysis the trends of incidence and mortality rates during 2000-2012. All in all, the burden of lung cancer is still not optimistic, especially in developing countries like China.
The overwhelming cause for high incidence of lung cancer is smoking [8], no matter active smoking or passive smoking [9]. Smoking was prevalent in western developed countries such as Europe, North America, Australia, Japan, South Korea, earlier in history, and reached its peak in the middle of the last century, so the burden of lung cancer is heavier. The prevalence of smoking among men had subsequently declined with the introduction of tobacco control policies in these countries, and the incidence of lung cancer in men had gradually declined [10], which is consistent with the trend was observed in this study.
However, the burden of lung cancer in women in these developed countries (United Kingdom, South Korea and Australia) kept plateauing and had a gradually upward trend, except for USA. This indirectly reflects that female smoking is still prevalence in developed countries. The heavy burden of lung cancer in China is partly due to the large population base. China has the largest number of smokers in the world and consumes about 40% of the world’s tobacco every year [11]. Meanwhile, exposure to secondhand smoke is also worthy of attention. Approximately 70% of Chinese people are exposed to secondhand smoking every year, and nearly lead to 60,000 lung cancer deaths (8%) [12]. China signed the WHO Framework Convention on Tobacco Control (FCTC) in 2003. Chinese government had issued a series of management regulations (Regulations on the control of smoking in public places) on tobacco control work, and had vigorously promoted the dangers of smoking in public media, so that the prevalence of male lung cancer had shown a significant decline in recent years. Although these regulations had initially shown positive effects, the efforts to control tobacco are obviously not strong enough, such as raising tobacco taxes or tobacco prices [13, 14].
Another important high-risk factor for lung cancer is ambient air pollution. A number of studies in European and American had found that the concentration of particulate matter (PM) in the environment, especially PM less than 2.5um (PM2.5), is closely related to the risk of lung cancer [15–17]. Therefore, outdoor air pollution was listed as a human carcinogen by the International Agency for Research on Cancer (IARC) in 2013 [18]. Ambient air pollution is also one of the reasons for the high incidence of lung cancer in developing countries such as China, India and Egypt. In recent years, with the rapid development of Chinese industrialization and transportation, especially the large use of coal and petroleum, a large number of harmful substances had been discharged into the atmosphere. The main causes of urban air pollution were the unreasonable energy consumption structure and low utilization rate. In 2012, China first proposed to monitor PM2.5 in key areas such as the Beijing-Tianjin-Hebei region, municipalities directly under the central government and provincial capital cities. In 2015, it was proposed that all prefecture-level cities carry out monitoring of PM2.5. The Chinese government had always been committed to promoting energy conservation and emission reduction, and had formulated corresponding measures. In 2020, China announced to the world the national goal of reaching a carbon peak by 2030 and striving to be carbon neutral by 2060. In addition, another factor contributing to the high incidence of lung cancer is indoor air pollution, including soot from household burning, heating or cooking. This might explain why the incidence of lung cancer among non-smoking East Asian women, including China and South Korea, remain high, especially between the ages of 40-59 [19–20].
Lung cancer is one of the malignant tumors with the worst prognosis. Lung cancer often were initially asymptomatic and typically discovered at advanced stages. People pay more and more attention to the early screening of lung cancer. A number of studies in Europe and America had shown that low-dose computed tomography (LDCT) scanning for high-risk individuals can help early detection of cancer [21, 22]. The National Comprehensive Cancer Network (NCCN), European Society of Radiology (ESR)/ European Respiratory Society (ERS), and the National Cancer Center of China had successively issued guidelines for lung cancer screening, and recommend risk assessments for people with smoking history, radon exposure, cancer history, family history of lung cancer in first-degree relatives and disease history (COPD or pulmonary fibrosis). Lung cancer screening agency experts recommend low-dose CT examinations for high-risk groups. Early diagnosis and early treatment can reduce the death rate of lung cancer [23–27]. This can explain why the incidence of lung cancer is higher in developed countries than in developing countries, and the mortality rate is lower.
Researches showed that the five-year survival rate of lung cancer in China was 18.6% in 2000, but increased to only 19.8% in 2010 [28–30]. In comparison, the five-year survival rate for lung cancer in Japan in 2010 was 32.9%, USA was 21.2% and South Korea was 25.1% [31]. The improvement of survival rate of lung cancer is not only related to cancer screening, but also to the medical level of the country and the pathological subtype of lung cancer. Lung cancer has traditionally been divided into two categories, non-small cell lung cancer (NSCLC) and small cell lung cancer, with the former accounting for about 85%. Lung adenocarcinoma is the most common pathological subtype [32]. Studies had shown that about 10-15% of NSCLC patients in Europe harbor the epidermal growth factor receptor (EGFR) gene mutation, and about 30-35% in Asia [33, 34]. About 60% of Asian, non-smoking female adenocarcinoma patients harbor the EGFR gene mutation [35, 36]. A series of studies had shown that patients with Ⅳ stage NSCLC harboring EGFR-sensitive mutations had significantly improved both progression-free survival (PFS) and overall survival (OS) using epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) compared with patients receiving standard chemotherapy [37–39]. Squamous cell lung cancer is insensitive to chemotherapy and radiotherapy except surgery. Small cell lung cancer has the highest degree of malignancy and the worst prognosis, which is easy to recurrence and distant metastasis. These two pathological subtypes had little choice in the previous systemic treatment. However, in recent years, lung cancer had entered the era of immunotherapy. For specific populations, no matter which subtype of lung cancer is likely to benefit from immunotherapy [40–42]. All in all, no matter the advanced treatment methods, excellent medical environment or perfect medical insurance system, these may be beyond the reach of many developing countries or poor areas.
This study had some limitations. Firstly, the data of this study comes from public databases, which lack detailed data such as pathological subtypes, disease stages, and treatment processes. If they can be combined with trend analysis, it will have more value for public health and clinical practice. Second, the latest data for the last 10 years cannot be obtained from this database.