Global cancer prevalence and its geographical distribution
Cancer is the abnormal growth of cells that spread to other parts of the body via metastases. It has been a topic of research worldwide since the early 1960s. Since then it has had a great impact on human health and economies worldwide (Jemal et al., 2010). Thus, global cancer prevalence has diversified from one geographical location to another. There are several cancer-causing reasons including lifestyle (external) factors, such as tobacco use, and excess body weight; internal factors, such as inherited genetic mutations, hormones and immune conditions (American Cancer Society, 2017).
Global statistics of cancer prevalence
Cancer is the second leading cause of death, with an estimated 8.8 million deaths in 2015 (WHO, 2017). It is expected that the number of new cases will rise by almost 70% over the next 2 decades (WHO, 2017). Among several risk factors, tobacco use accounted for 22% of cancer deaths (WHO, 2017). The majority of these cases were from developing countries (American Cancer Society, 2015). A marginal reduction in smoking, as well as improvement in early detection and treatment, is responsible for the decrease in cancer prevalence and mortality in the last few years. The most common causes of mortality are cancers of the Lung (1.69 million deaths), Liver (788 000 deaths), Colorectal (774 000 deaths), Stomach (754 000 deaths) and Breast (571 000 deaths). Globally, nearly 1 out of 6 disease-related deaths is caused by cancer.
The major cause of death from cancer are the 5 leading behavioural and dietary risks i.e. tobacco use, alcohol use, high body mass index, low fruit and vegetable intake and lack of physical activity. Cancer-causing infections, such as hepatitis and human papillomavirus (HPV), are responsible for up to 25% of cancer cases in low- and middle-income countries (Jemal et al, 2010).
Cancer prevalence in India
Statistics in India showed that the estimated number of people living with the disease is around 2.5 million. Every year, over 700,000 new cancer cases are registered. Out of this, deaths have occurred in 5,56,400 cases. A maximum number of deaths has occurred in the age group 30-69 years, most of whom are men (Saranath & Khanna, 2014).
The top five cancers in men i.e. Oral cavity cancer, Lung cancer, Stomach cancer, Colorectal cancer and Pharynx cancer. And in women Breast cancer, Cervix cancer, Colorectal cancer, Ovary cancer and oral cavity cancer account for 47.2% of all cancers (Dikshit et al., 2012). These cancers can be prevented if screened for and detected early and treated at an early stage. This could help significantly reduce the death rate from these cancers.
The table below shows the frequency of cancer occurrence across different parts of the world (American Cancer Society, 2017).
|Continent based||Cancer incidents tally (as in 2008-2012)||Cancer incidents tally (as in 2013-2016)|
|North America||152.2 cases/100,000 person-years||219 cases/100,000 person-years|
|Asia||315.6 cases/100,000 person-years||404 cases/100,000 person-years|
|Africa||79 cases/100,000 person-years||141.7 cases/100,000 person-years|
|South America||87.4 cases/100,000 person-years||138.2 cases/100,000 person-years|
|Australia and Oceania||293.5 cases/100,000 person-years and 60 cases/100,000 person-years||483 cases/100,000 person-years and No Data for Oceania|
Factors contributing to geographic variations in cancer prevalence
Among the eight most common cancers prevalent in the world, there is evidence of global disparities in cancer incidence and mortality, which are likely due to the complex interactions of non-modifiable (i.e., genetic susceptibility and ageing) and modifiable risk factors (i.e., tobacco, infectious agents, diet, and physical activity). Indeed, global cancer disparities are inevitable, when risk factors among populations are intertwined with differences in individual behaviours, cultural beliefs and practices, socioeconomic conditions, and healthcare systems (Kamangar, Dores, & Anderson, 2006).
According to International Agency for Research on Cancer (IARC), cancer is caused by the interaction between a person’s genetic factors and 3 categories of external agents, including:
- physical carcinogens, such as ultraviolet and ionizing radiation,
- chemical carcinogens, such as components of tobacco smoke, aflatoxin (a food contaminant), arsenic (a drinking water contaminant); and
- biological carcinogens, such as infections from certain viruses, bacteria, or parasites.
The most important factors that differentiate cancer prevalence globally are variations in age, the structure of the population, the prevalence of risk factors, the availability and use of diagnostic tests and the availability and quality of treatment (American Cancer Society, 2015).
Prevention and cure
Despite significant reductions in cancer mortality in many countries, cancer prevalence poses a barrier to future development. Cancer prevention and treatment interventions offer hope that this threat can be controlled. Most cancer prevention efforts have a much broader impact than just reducing cancer incidence. By avoiding risk factors and implementing existing evidence-based prevention strategies, nearly 30–50% of cancers can currently be prevented. Through early detection of cancer and management of patients who develop cancer, the cancer burden can also be reduced. Many cancers have a high chance of being cure if diagnosed early and treated adequately.
- American Cancer Society (2015) Global Cancer Facts & Figures, American Cancer Society. doi: 10.1002/ijc.27711.
- American Cancer Society. (2017). Cancer Facts and Figures 2017. Genes and Development, 21(20), 2525–2538. https://doi.org/10.1101/gad.1593107
- Jemal, A. et al. (2010) ‘Global patterns of cancer incidence and mortality rates and trends.’, Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology. American Association for Cancer Research, 19(8), pp. 1893–907. doi: 10.1158/1055-9965.EPI-10-0437.
- Dikshit, R., Gupta, P. C., Ramasundarahettige, C., Gajalakshmi, V., Aleksandrowicz, L., Badwe, R., … Jha, P. (2012). Cancer mortality in India: A nationally representative survey. The Lancet, 379(9828), 1807–1816. https://doi.org/10.1016/S0140-6736(12)60358-4.
- Nair, M.K., Varghese, C. and Swaminathan, R., 2005. Cancer: Current scenario, intervention strategies and projections for 2015. NCHM Background papers-Burden of Disease in India, pp.219-25.
- Roser, M., & Ritchie, H. (2017). Cancer. Retrieved from https://ourworldindata.org/cancer.
- Saranath, D., & Khanna, A. (2014). Current Status of Cancer Burden: Global and Indian Scenario. Biomed Res J, 1(1), 1–5.