Changing profiles of cancer burden worldwide and in China: a secondary analysis of the global cancer statistics 2020

Introduction

Cancer is one of the leading causes of death globally, but its burden is not uniform.^[1] The cancer burden has grown over time in both developed and developing countries due to the complex reasons involved, which include aging and burgeoning population, accelerating socioeconomic development, and changes in the prevalence of associated risk factors.^[2,3] With the population expanding and aging worldwide, cancer is the primary cause of premature death and decreases life expectancy in many countries.^[4] However, disparities in the patterns of cancer diagnoses have been observed. Countries with varying human development index (HDI) have different profiles of common cancer types. For example, colorectal and prostate cancers are common among men in high HDI areas, whereas cervical cancer occurs more frequently in women in low HDI areas.^[5] Moreover, standardized incidence rates for some of the leading cancer types are 200% to 300% higher in transitioned economies than in transitioning economies.^[2] Countries at the transitioning stage face a predominance of infection-related cancers and an increasing cancer burden that is associated with Western lifestyles.

China is one of the countries in the transitioning stage of cancer.^[6] The incidence and mortality profiles of China are changing from those of developing countries to those of developed countries.^[7] Since China has a population of 1.4 billion, even minimal increases in incidence or mortality rates indicate great threats to individuals at risk and a significant economic burden. Cancer transition increases the difficulty of cancer prevention and control.^[8] Therefore, an understanding of the contemporary cancer transition and an analysis of the changing profiles of China's cancer burden are urgently needed to ensure that targeted cancer prevention and control could be tailored and implemented.

GLOBOCAN 2020 provided updated estimates of cancer incidence and mortality at the end of 2020. It is estimated that the number of new cancer cases reached 19.3 million globally, and nearly 10 million people died from cancer in 2020.^[9] Furthermore, female breast cancer displaced lung cancer and became the most substantially diagnosed cancer for the first time. The current study provides an overview of cancer incidence and mortality in 2020 based on the most recent data compiled by the International Agency for Research on Cancer (IARC), the changing profiles of leading cancer types worldwide and in China, projected cancer incidence and mortality over the next two decades, and the implications of the above factors for cancer research and control.

Methods

Results

Discussion

With the increasing incidence and mortality, cancer remains a primary public health problem. The changing profiles of the most common cancer types revealed that breast cancer replaced lung cancer as the most diagnosed cancer globally in 2020. The incidence of breast cancer has increased in both high-HDI and low-HDI countries, and the ASIR in more developed regions is 2 to 4 times that in less developed regions.^[1,9] Potential reasons for this increase may be ongoing changes in reproductive practices, including declining fertility rates, postponement of the first childbearing, and breastfeeding for shorter durations.^[12] Excess body weight and a high body mass index are also associated with increased breast cancer risk among older women, especially after menopause.^[13,14] Moreover, variations in breast cancer incidence also reflect disparities in the prevalence and distribution of risk factors in different areas. Countries undergoing rapid societal and economic development are more likely to experience changes in the breast cancer profiles of their population.^[15]

We also observed rank changes in the mortality attributable to liver cancer, which is currently the second leading cause of cancer-related deaths globally. Etiologically, hepatitis B/C virus infections and alcohol use are responsible for more than 80% of liver cancer deaths.^[16] Previous studies illustrated that liver cancer mortality varies considerably depending on the patient's age groups, sex, ethnicity, educational attainment, and geographic area.^[17,18] Targeted interventions, including vaccination, disruption of hepatitis virus transmission, antiviral treatment, and reduced alcohol consumption, are urgently needed to halt the growing burden of liver cancer.

In China, comparing new cases and deaths by cancer type between 2015 and 2020 exhibits the changing profiles of the cancer burden. Lung cancer remains the most common cancer type and the leading cause of cancer-related deaths. Tobacco consumption, air pollution, and occupational exposure are the primary carcinogens that contribute to lung cancer incidence.^[19] China is experiencing cancer transitioning stage with substantial increases in the new cases of colorectal cancer and female breast cancers. In high-HDI countries, lung, colorectal, and female breast cancers, possibly associated with a Westernized lifestyle, are responsible for nearly one-half of the total cancer incidence.^[5] China's cancer incidence profile is becoming similar to that of high-HDI countries. However, the leading causes of cancer-related mortality remained consistent between 2015 and 2020. The cancer mortality rate is higher in China than in developed countries. In addition to lung cancer, gastrointestinal cancers account for 45% of the cancer-related deaths in China, whereas the corresponding figure is much lower in developed countries (eg, the USA and the UK).^[7] A possible explanation for this finding is that gastrointestinal cancers may have poorer prognoses, and late-stage presentation may be more common in China. An updated overview of cancer epidemiology would improve our understanding of the cancer patterns and possibly help tackle cancer burden more efficiently in China.

The analysis of projected incidence and mortality indicated that the cancer burden will continue to increase over the next 20 years. Much is still required to fight against cancer. However, a “one-size-fits-all” strategy for cancer prevention and control does not seem to be effective. Consider China as an example, the level of cancer awareness is inversely associated with cancer risk in rural China.^[20] Health promotion and education that disseminate cancer knowledge and improve cancer development perceptions are crucial in real practice.^[21] As potentially modifiable risk factors have been identified across all provinces in China,^[22] tailored healthier lifestyles should be persistently recommended across different areas. Organized cancer screening programs funded by the Chinese government have been implemented for several years in rural and urban China to explore appropriate strategies for early cancer detection.^[23,24] Comprehensive strategies, including vaccination programs and tobacco control policies, also need to be developed.^[25]

The estimated incidence and mortality vary substantially across continents and countries. In addition to several socioeconomic and lifestyle factors, it is noteworthy that the coverage and data quality of the cancer registry play a critical role in cancer surveillance.^[26] Currently, high-quality registry data are not extensively available in most low- and middle-income countries. For instance, cancer registries cover only small proportions of the population (less than 10%) in Latin America and Asia, whereas the corresponding figure is 98% in the USA.^[27,28] China's national cancer registry has made remarkable improvements in data representativeness and quality since its establishment in 2002.^[29] The total number of local population-based cancer registries has increased significantly from 501 in 2015 to 1152 in 2020, presently covering up to 598 million people in China.^[3,30] However, the data quality in these registries is inconsistent. Persistent efforts should be devoted to improving and achieving more reliable national cancer data, laying a solid foundation for precise burden estimates and evidence-based cancer control programs.

GLOBOCAN 2020 has shown that it is vital for global cancer control to deliver cancer prevention and care in transitioning countries.^[9] China, a transitioning country, bears a massive burden of cancer incidence and mortality. This study depicts the most recent changing profile of the cancer burden, particularly in China, and compares the cancer data of China with those of other regions. Future implications for tailored policies and targeted practices on cancer control in China may be drawn from the findings of this study. However, potential limitations should be noted when interpreting the findings. Although GLOBOCAN 2020 provides reasonably accurate estimates of recent cancer data, caution should be exercised when evaluating the real burden under the impact of the global COVID-19 pandemic on decreased access to health care and delayed cancer diagnosis. Second, the cancer burden varies considerably according to sex, age group, race/ethnicity, and geographic location.^[31] Cancer disparities should be addressed explicitly in research to enable customize targeted cancer control programs. Additionally, by performing our analysis of the future cancer burden using only five years of data, we did not account for other data sources and variables, which could have improved our understanding of the burden and related trends in the near future.

Conclusions

The burden of breast cancer is increasing globally. China is undergoing cancer transitioning with an increasing burden of lung cancer, colorectal cancer, and female breast cancer. In China, cancer mortality is high, and gastrointestinal cancers account for 45% of all cancer deaths in 2020. An overview of the updated cancer epidemiology would renew our understanding of the recent cancer burden. Comprehensive strategies, including health education, dissemination of essential cancer knowledge, advocacy of healthy lifestyle, effective cancer screening, vaccination programs, and tobacco-control policies, need to be tailored to target China's cancer pattern.

Conflicts of interest

None.