Clinical Cancer: Breast cancers worldwide reached 2.2 million in 2020

Clinical Cancer: Breast cancers worldwide reached 2.2 million in 2020.   Recently, the “Journal of Clinical Cancer” released the “Global Cancer Statistics 2020”. The results show that the number of new breast cancer cases worldwide in 2020 has exceeded that of lung cancer, becoming the cancer with the highest number of diagnoses. Lung cancer ranked second and colorectal cancer ranked third.

According to Hyuna Sung, chief scientist and cancer epidemiologist of the American Cancer Society, there will be approximately 19.3 million newly diagnosed cancer cases worldwide and nearly 10 million deaths in 2020. Approximately 2.3 million (11.7%) of newly diagnosed female breast cancers were newly diagnosed, ranking first. This is followed by lung cancer (11.4%), colorectal cancer (10.0%), prostate cancer (7.3%) and stomach cancer (5.6%). The female breast cancer mortality rate ranked fifth, with a total of 685,000 deaths.

The incidence of breast cancer in developed countries is 88% higher than that in developing countries (55.9 per 100,000 and 297,000 per 10,000, respectively). Australia, New Zealand, Western Europe, and North America have the highest incidence, while Central America, East Africa, and Central and South Asia have the lowest incidence. However, the mortality rate in developing countries is 17% higher than that in developed countries, and the mortality rate in Melanesia, West Africa, and the Caribbean is the highest.

Countries with higher human development index, that is, higher life expectancy, education level and quality of life, the higher incidence of breast cancer is related to reproductive and hormonal risk factors, including earlier menarche, later menopause, less fertility, and less breastfeeding , Menopausal hormone therapy and oral contraceptives, as well as drinking, excess weight, lack of exercise and other bad habits. The abnormally high incidence of BRCA1 and BRCA2 mutations also led to a significantly higher incidence in Israel and Eurasia.

In the 1980s and 1990s, the incidence of breast cancer increased rapidly in many countries in North America, Oceania, and Europe, which was related to changes in breast cancer risk factors, but it may also be due to the increase in the popularity of mammogram screening. At the beginning of the 21st century, the incidence rate in these areas remained stable or declining, which was related to the decrease in the use of menopausal hormone therapy, and it may also be due to the plateau of mammography screening.

Since 2007, the incidence of breast cancer in the United States has increased by an average of 0.5% per year, and there has also been an increasing trend in many countries in Europe and Oceania. According to the comparison of tumor marker data, the incidence of cancer patients with positive estrogen receptors increased, and the incidence of receptor negative decreased. Analysis shows that overweight and obesity have a stronger relationship with estrogen receptor-positive cancer. X-ray screening can give priority to screening for slow-growing receptor-positive breast cancer.

Several breakthroughs in the popularization and treatment of breast cancer have brought better treatment effects to patients in these high-risk areas, and their mortality has been declining since the late 1980s. In contrast, high-income Asian countries such as South America, Africa, Japan, and South Korea used to have low incidence of breast cancer. However, with economic growth, the proportion of female laborers has increased, and lifestyle changes such as delayed childbirth, overweight and lack of exercise, etc. The incidence of breast cancer in the region gradually approaches that of Western countries.

Sung said that the global promotion of breast cancer primary prevention programs is an important starting point for reducing the burden of breast cancer disease. Reducing the rate of overweight and alcohol consumption, and encouraging sports and breastfeeding will help curb the global increase in breast cancer incidence. The World Health Organization recommends that if conditions permit, each country should conduct an organized mammogram screening for women aged 50-69. The American Cancer Society recommends that women aged 45-54 should be screened every year, women aged 40-44 should be screened every year, and that they should be screened every two years when they are over 55. As long as the overall health is good and the life expectancy is greater than 10 years, screening should be continued.

The author points out that mammogram screening has limitations and may also lead to overdiagnosis and overtreatment. We should use risk prediction models, adopt reasonable screening strategies to improve the cost-effectiveness of screening, and evaluate the accessibility and practicality of these stratified screening projects in the general population.

(source:internet, reference only)

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