Breast cancer in women has surpassed lung cancer as the most commonly diagnosed cancer in the world, according to a new report.
The paper, published in the CA: A Cancer Journal for Clinicians on Thursday, estimates that there were about 2.3 million new cases of female breast cancer last year, making up 11.7% of all new cancer cases. Meanwhile, lung cancer made up 11.4% of total cases diagnosed, according to the new report.
Until now, lung cancer had been the most diagnosed in previous reports covering the last two decades, said Hyuna Sung, principal scientist and cancer epidemiologist at the American Cancer Society, who was an author of the paper.
"The change of the rank signals the epidemiologic transition of cancers," Sung told CNN. "That was quite surprising news for us."
Breast Cancer Leads in Cases, Lung Cancer Leads in Deaths
There were 2.3 million new cases of breast cancer and 2.2 million new cases of lung cancer in 2020, according to the new report.
In 2018, the most recent year with available data, lung cancer was in the lead -- there were 2,088,849 new cases of breast cancer and 2,093,876 new cases of lung cancer at that time.
Sung said in an email to CNN on Thursday that there has been an increase in breast cancer awareness, but mammogram screenings may not explain the full rise of breast cancer diagnoses over time.
"The increasing trend of breast cancer is likely to reflect the increase in the prevalence of breast cancer risk factors such as excess body weight, physical inactivity, alcohol consumption, postponement of childbearing, fewer childbirths, and less breastfeeding," Sung said.
Researchers from the American Cancer Society in Atlanta and the International Agency for Research on Cancer in France wrote in the report that lung cancer still ranked as the leading cause of cancer death among both men and women combined, with an estimated 1.8 million deaths, making up 18% of all cancer deaths.
Lung cancer was the leading cause of cancer deaths among men, making up 21.5% of men's cancer deaths. Whereas, breast cancer was the leading cause of cancer death among women at 15.5%.
'The Burden of Cancer... Is Rapidly Growing Worldwide'
The report is based on cancer incidence and mortality data from the International Agency for Research on Cancer. Overall, the data suggest that there were an estimated 19.3 million new cases and 10 million cancer deaths worldwide in 2020.
The five most commonly diagnosed cancers, according to the report, were: female breast cancer, lung cancer, colorectal cancer, prostate cancer, and stomach cancers.
The five leading causes of cancer death, the data showed, were: lung, colorectal, liver, stomach, and female breast cancer.
These estimates do not reflect the potential impact that Covid-19 could have had on cancer diagnoses or deaths since the estimates draw from extrapolations of cancer data from previous years.
"Nobody knows the full extent of the impact of the pandemic on cancer statistics yet," Sung said. "But there are many studies that suggest we are already seeing delays in diagnosis and treatment."
Looking ahead, the new report estimates that the global burden of cancer is projected to reach 28.4 million cases in 2040 -- marking a 47% rise from last year.
In the past two decades, according to the World Health Organization, the number of people diagnosed with cancer climbed from an estimated 10 million in 2000 to 19.3 million in 2020.
Now, about 1 in 5 people worldwide will develop cancer during their lifetime, the WHO noted.
"The burden of cancer incidence and mortality is rapidly growing worldwide, and 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," Freddie Bray, senior author of the report and head of the section of cancer surveillance at the International Agency for Research on Cancer, said in a news release.
"Effective and resource-sensitive preventative and curative interventions are pertinent for cancer diagnosis," Bray said. "Tailored integration into health planning can serve to reduce the global burden of cancer and narrow the evident cancer inequities between transitioning and transitioned countries observed today."