The numbers highlight the importance of early detection, researchers said.
The report, called "Global Cancer Statistics 2020," was written by the American Cancer Society (ACS) and the International Agency for Research on Cancer (IARC) and used data from the latter's Global Cancer Observatory (GLOBOCAN). The organizations found that there were 19.3 million new cancer cases in 2020; of these, 2.3 million (11.7%) were female breast cancer.
The incident rate of cancer is tied to socioeconomic factors, noted a team led by Hyuna Sung, PhD, principal scientist at the ACS, with women in "transitioning" countries (i.e., those shifting from a centrally planned economy to a free market structure) experiencing increases in incidence compared with their already-transitioned counterparts.
"Overall, the burden of cancer incidence and mortality is rapidly growing worldwide; this reflects both aging and growth of the population as well as changes in the prevalence and distribution of the main risk factors for cancer, several of which are associated with socioeconomic development," Sung's group wrote.
Female breast cancer has now exceeded lung cancer as the leading cause of global cancer incidence in 2020, and it is the fifth leading cause of cancer mortality around the world, the report authors found. Breast cancer ranks first for incidence in 159 out of the 185 countries included in the report.
|Top 10 cancer sites of new cases worldwide, 2020
||Percentage of total new cases
|Nonmelanoma of skin
Breast cancer rates are increasing in countries where its incidence has tended to be low -- such as those in South America, Africa, and Asia -- but also high-income Asian countries (Japan and South Korea), the investigators wrote.
"Dramatic changes in lifestyle, sociocultural, and built environments brought about by growing economies and an increase in the proportion of women in the industrial workforce have had an impact on the prevalence of breast cancer risk factors -- the postponement of childbearing and having fewer children, greater levels of excess body weight and physical inactivity -- and have resulted in a convergence toward the risk factor profile of western countries and narrowing international gaps in breast cancer morbidity," the group noted.
Cancer is the primary cause of death around the world, with one in five people developing the disease in their lifetime, according to the authors. The report found that lung cancer remains the leading cause of cancer death, with 1.8 million deaths per year (18%), followed by colorectal (9.4%), liver (8.3%), stomach (7.7%), and female breast (6.9%) cancers.
But the death rate from breast cancer among women in transitioning countries is higher compared with their peers in developed countries -- despite the fact that the incidence rate among women in transitioning countries is much lower compared with their free-market counterparts.
|2020 breast cancer death and incidence rates worldwide, "transitioning" versus "transitioned" countries
|Breast cancer death rates per 100,000 women
|Breast cancer incidence rates per 100,000 women
Why the higher death rates? Perhaps because women in transitioning countries present with more advanced disease, Sung and colleagues said in the ACS statement.
"As the poor outcome in these countries is largely attributable to a late-stage presentation, efforts to promote early detection, followed by timely and appropriate treatment, are urgently needed through the implementation of evidence-based and resource-stratified guidelines," they said.
Cancer incidence will likely get worse over the next two decades, Sung's team warned. The report estimates 28.4 million new cancer cases worldwide in 2040, up 47% from 2020, and transitioning countries will experience a higher relative increase (64% to 95%) compared with their already-transitioned counterparts (32% to 56%).
Cancer prevention efforts must increase if the disease is to be contained, the team concluded.
"The growing rate of incidence could overwhelm healthcare systems, if left uncontrolled," it said in the ACS statement. "Efforts to build a sustainable infrastructure for the dissemination of proven cancer prevention measures and the provision of cancer care in transitioning countries are critical for global cancer control."
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