Cancer cases are expected to increase by 60% globally in 2040, based on projected population and aging alone
There are still 1.1 billion smokers worldwide, and tobacco causes more preventable cancer deaths than any other risk factor, says the third edition of Cancer Atlas
Cancer is a major public health issue, and its burden is set to spiral. The global cancer burden is expected to increase significantly — about 60% — by 2040, with tobacco being the leading preventable cause of cancer.
With 18.1 new million cases in 2018, 29.4 million cases can be expected by 2040 due to the aging and growth of the population, according to the third edition of the Cancer Atlas, which is a comprehensive global overview of cancer around the globe.
There were an estimated 18.1 million cases globally and 9.6 million cancer deaths in 2018 (including non-melanoma skin cancers), with one in four men and one in five women developing the disease, and one in eight men and one in 11 women dying from it. Besides, there were 43.8 million persons living with cancer in 2018 who were diagnosed within the last five years.
More broadly, cancer has become a leading cause of death over the last few decades. Cancer is the leading or second-leading cause of premature death (under age 70) in 91 countries worldwide. In terms of premature mortality (defined as death in ages 30–69 years), in the year 2016, cancer was the leading cause of death in 55 (largely high-income) countries, but second (mainly to cardiovascular disease) in an additional 79 countries. With rates of cardiovascular mortality in decline in many countries due to highly successful prevention and treatment, cancer is set to become the leading barrier to increasing life expectancy in this century.
"Cancer ranks as the first or second leading cause of premature death (among those 30–69 years of age) in 134 countries of the world. The global cancer burden is dominated by Europe, China, and Northern America," says the report by the American Cancer Society (ACS), the Union for International Cancer Control (UICC), and International Agency for Research on Cancer (IARC). The findings were released at the World Cancer Leaders' Summit in Nur-Sultan, Kazakhstan.
"Half of the new cancer cases and cancer deaths in the world occur in Asia. China, with the largest population size in the region and worldwide — 1.4 billion inhabitants, representing 19% of the global population in 2018 — has the greatest global proportion of new cases (4.3 million cases, 24% of the total) and deaths (2.9 million deaths, 30%). Northern America is second in terms of new cases (2.4 million, 13%) and fourth for cancer deaths (0.7 million, 7%). Close to one-fourth of all new cases globally (4.2 million) and one-fifth of deaths (1.9 million) occur in Europe, despite the region representing less than one-tenth of the global population," says the report.
Globally, for both sexes combined worldwide, lung cancer continues to be the most commonly diagnosed cancer (2.1 million, 12% of the total) and the leading cause of cancer death (1.8 million, 18%) because of its poor prognosis, say researchers.
Female breast cancer is the second most common cancer overall (2.1 million, 12%) but the fifth leading cause of cancer death (627,000, 7%) because of its relatively favorable prognosis. "As such, it is the most prevalent cancer worldwide - 6.9 million women living within five years of their breast cancer diagnosis," the findings state.
Colorectal cancer is the third most frequently diagnosed cancer globally, but second only to lung cancer in terms of mortality (1.8 million cases and 881,000 deaths). This is followed by prostate cancer, which is the fourth most frequently diagnosed cancer, while stomach and liver cancer remain major causes of cancer death in 2018.
Childhood cancer burden
Each year, about 270,000 cancer cases are diagnosed in children. Currently, the five-year survival from childhood cancer in high-income countries is greater than 80%, but it can be as low as 20% in low-income countries, say experts. Further, over half of long-term survivors of childhood cancer experience chronic health conditions.
"Cancers occurring in childhood and adolescence differ markedly from cancers in adults in their incidence and tumor characteristics. Worldwide, the average annual incidence in children aged less than 15 years is 140 new cases per million children, although there are three-fold variations between world regions and ethnic groups," says the team.
The most common cancers in children are leukemia and lymphoma, while the major cancers among adults, such as carcinoma of the lung, breast, or colon, are rare in children.
The experts say that with interventions to improve early diagnosis and adherence to appropriate treatment, childhood cancer survival can be increased to 60% in low-income countries, saving almost one million children's lives over a decade.
Many risk factors can be prevented
Tobacco use, infectious agents, unhealthy diet, excess body weight, physical inactivity, and alcohol consumption account for the majority of cancer deaths caused by known risk factors. However, many of the known risk factors for cancer can be prevented, say experts.
According to the researchers, tobacco use is the leading preventable cause of cancer worldwide. An estimated 1.3 billion people use tobacco products worldwide. The majority - about 1.1 billion - use smoked tobacco products, chiefly as manufactured or hand-rolled cigarettes.
Smoking, says the team, causes multiple cancer types, and smokeless tobacco causes cancers of the oral cavity, esophagus, and pancreas. In 2017, smoking was responsible for an estimated 2.3 million cancer deaths globally (24% of all cancer deaths), with an additional 190,000 cancer deaths due to smokeless tobacco and secondhand smoke.
"All smoked and traditional smokeless tobacco products cause cancer. Although lung cancer is the most common cancer caused by cigarette smoking, at least 19 other cancer sites or subsites are designated as causally related to smoking. Smoked tobacco products cause even more deaths from vascular and respiratory conditions than from cancer. Cessation of smoking dramatically reduces risks compared to continued smoking," says the study.
Progress in tobacco control legislation over the last decade means 1.5 billion people in 55 countries are now protected by smoke-free legislation.
Infectious agents are responsible for an estimated 15% of all new cancer cases worldwide, but the proportion varies, ranging from around 4% in many very high-income countries to more than 50% in several sub-Saharan African countries. The four primary infectious agents - which together account for more than 90% of all infection-related cancers - are Helicobacter pylori (770,000 cases globally in 2012), human papillomavirus (HPV) (640,000), hepatitis B virus (HBV) (420,000), and hepatitis C virus (HCV) (170,000).
"Helicobacter pylori causes 90% of stomach cancers, half of which occur in China alone. The HPV infection is a necessary cause of cervical cancer, which is the leading cause of cancer death among women in many less-developed regions of the world because of lack of screening," says the report.
HPV infection is also responsible for a proportion of vulvar (25%), vaginal (78%), anal (88%), penile (50%), oropharyngeal (31% on average, but much higher in North America and Northern Europe), oral cavity (2.2%) and laryngeal cancer (2.4%). Globally, HBV and HCV infections account for 56% and 20% of liver cancer deaths, respectively.
"Powerful prevention tools exist for infection-related cancer, including HPV and HBV vaccines, screening for HPV-driven cervical precancer, and drugs to treat HBV, HCV, Helicobacter pylori, and HIV infections," say experts.
An unhealthy diet, excess body weight, and physical inactivity cause multiple types of cancer and are emerging risk factors for cancer worldwide. Experts say that the cancer burden associated with these risk factors is expected to grow in most parts of the world, particularly in parts of the Middle East and several other low- and middle-income countries in parts of Asia and Oceania because of the obesity epidemic.
"Excess body weight increases the risk of 13 types of cancer and in 2012 accounted for 3.6% of all new cancer cases among adults worldwide. The prevalence of excess body weight is rising worldwide: in 2016, an estimated 39% of men and 40% of women aged 18 years and older, and 27% of boys and 24% of girls aged 5-18 years, were obese. High amounts of sugar-sweetened beverages and sedentary behaviors, including screen-time, increase the risk of excess body weight," says the study.
The report also states that approximately 3 to 6% of all cancers globally are caused by exposure to carcinogens in the workplace. Outdoor air pollution causes over half a million lung cancer deaths and millions of deaths from other diseases each year.
According to the experts, "resource-appropriate, broad application of known interventions" in each country can significantly reduce the disease burden prevent a substantial proportion of cancer deaths.
The report says existing cost-effective interventions such as surgery, radiotherapy, and access to essential oncologic drugs can significantly improve cancer survival worldwide. Currently, 8 million people die annually due to poor-quality care in low- and middle-income countries (LMICs), including many due to cancer, says the team. Health promotion must address the environmental, economic, and social factors that influence health behaviors, they recommend.
"This much is clear. We simply must do better to ensure everyone can benefit from advances in the fight against cancer. Progress is not only possible but also achievable," states Gary Reedy, ACS chief executive officer in the report.