Global breast cancer burden rising fastest in low-income countries

Despite recent advancements in breast cancer treatments, new breast cancer cases in women are predicted to rise by a third globally from 2.3 million in 2023 to more than 3.5 million in 2050. Similarly, yearly deaths from the disease are projected to surge 44%, from around 764,000 to 1.4 million, with disproportionate impact in countries with limited resources, according to a major new analysis from the Global Burden of Disease Study Breast Cancer Collaborators, published in The Lancet Oncology. 

Importantly, the findings suggest that maintaining a healthy lifestyle, including not smoking, getting sufficient physical activity, lowering red meat consumption, and having a healthy weight may prevent over a quarter of healthy years lost to illness and premature death due to breast cancer worldwide. 

"Breast cancer continues to take a profound toll on women's lives and communities," said lead author Kayleigh Bhangdia from the Institute for Health Metrics and Evaluation (IHME), University of Washington, USA. "While those in high-income countries typically benefit from screening and more timely diagnosis and comprehensive treatment strategies, the mounting burden of breast cancer is shifting to low- and lower middle-income countries where individuals often face later-stage diagnosis, more limited access to quality care, and higher death rates that are threatening to eclipse progress in women's health." 

Using data from population-based cancer registries, vital registration systems, and interviews with family members or caregivers of women who have died from breast cancer, the new analysis provides an updated global, regional, and national analysis of the female breast cancer burden and risk factor estimates from 1990 to 2023 in 204 countries and territories, with forecasts up to 2050. Importantly, the study also estimates the number of years of healthy life that women with breast cancer have lost to illness, disability, and premature death.

Rates of new cases remain highest in HICs, but growing fastest in LICs

Breast cancer remains the most common cancer among women worldwide, with an estimated 2.3 million new breast cancers diagnosed worldwide in women in 2023 (with 73% or 1.67 million cases occurring in high- and upper-middle-income countries) and 764,000 resulting deaths (with 39% or 300,000 deaths occurring in low- and lower-middle-income countries). 

When global cases and death rates are adjusted to account for differences in age (to allow comparisons between countries and over time), the study reveals striking inequalities in the burden of breast cancer. For example, in 2023, breast cancer age-standardised incidence rates were on average highest in high-income countries (HICs), including Monaco, Andorra, France, Germany and Ireland (100 new cases per 100,000 women or higher), and lower in low- and middle-income countries (LMICs), including Afghanistan, Somalia, and Mozambique (13 new cases per 100,000 women or lower) in 2023. 

However, age-standardised rates of new cases have risen sharply (up 147% on average) since 1990 in low-income countries (LICs), but remained stable in HICs, highlighting the disproportionate growth occurring in settings with lower resources (see table 1 in the paper). 

Moreover, between 1990 and 2023, age-standardised death rates from breast cancer in HICs fell on average 30% to 16 deaths per 100,000 women, but almost doubled in LICs to 24 deaths per 100,000 women, exposing likely disparities in timely diagnosis and access to quality treatment. 

Globally, the number of years of healthy life lost due to poor health and early death more than doubled from 11.7 million years in 1990 to 24 million years in 2023. However, although women in low- and lower-middle-countries account for 27% (around 628,000) of new cases globally, they contribute to more than 45% of all the ill-health and early deaths from breast cancer globally (nearly 11 million years of healthy life lost). 

"LMICs are hit hardest by escalating breast cancer burden as many of these nations grapple with lifestyle and demographic changes alongside health systems that are less equipped than ideal to respond, with shortages of radiotherapy machines, chemotherapy drugs, and pathology labs, and standard treatments that can be quite costly," explained co-author Dr Olayinka Ilesanmi, a physician and epidemiologist from Nigeria working for the Africa CDC. "Although survival continues to improve in HICs, reflecting success in breast cancer screening, diagnosis, and treatment, even within HICs, outcomes can still depend on where a woman lives." 

Rise in pre-menopausal breast cancer 

Globally, three times as many new breast cancer cases were diagnosed in women aged 55 or older in 2023 (161 vs 50 new cases per 100,000 women) compared to women aged 20-54 years. However, rates of new cases have risen in women aged 20-54 years old (up 29%) since 1990, with rates in older women not changing substantially-these differences may reflect changing age patterns as well as changes in risk factors, which vary between pre- and post-menopausal women. 

Impact of uncontrolled risk factors 

In 2023, 28% of the global breast cancer burden (6.8 million years of healthy life lost to disability, illness and early death) was linked to six potentially modifiable risk factors. High red meat consumption had the biggest impact (linked to nearly 11% of all healthy life lost), followed by tobacco use (including second-hand smoke; 8%), high blood sugar (6%), high body mass index (BMI; 4%), and high alcohol use and low physically activity (both 2%). 

Substantial progress has been made in reducing the global breast cancer burden linked to high alcohol use and tobacco between 1990 and 2023, which declined by 47% and 28%, respectively, while the breast cancer burden linked to other risk factors did not indicate the same progress over time. 

"With more than a quarter of the global breast cancer burden linked to six modifiable lifestyle changes there are tremendous opportunities to alter the trajectory of breast cancer risk for the next generation," said co-senior author Dr Marie Ng, Affiliate Associate Professor at IHME and Associate Professor at National University of Singapore. "Targeting known risk factors through public health policies and making healthier choices more accessible, while working with individuals to take action to reduce obesity and high blood sugar, is crucial to halting the rise in breast cancers worldwide." 

Ensuring all women have an equal chance to survive breast cancer 

Even with the best prevention policies, millions of women will still develop breast cancer, which makes closing the care gap an urgent priority. The authors stress that with fair access to care in low-resource settings, investment in innovative therapies, and strong political will, there is an opportunity to ensure that all women have an equal chance to overcome breast cancer. 

As Dr Lisa Force, co-senior author from IHME explained, "Collaborative efforts are needed to ensure well-functioning health systems capable of early diagnosis and comprehensive treatment of breast cancer in all countries. Reducing the cost of breast cancer therapies and ensuring that universal health coverage includes breast cancer care essentials would also be valuable in protecting patients from catastrophic costs and improving outcomes." 

While the study uses the best available data, the authors note that the estimates are constrained by a lack of high-quality cancer registry data, particularly in countries with limited resources, highlighting the need to increase investments in cancer surveillance systems. They also note that information on cancer stage at diagnosis and subtype are not included in the analysis despite their distinct survival patterns and resource implications due to data limitations, and the analysis does not analyse the impact of the COVID-19 pandemic or recent conflicts on the disease burden. 

Writing in a linked Comment, Professor Yeon Hee Park from Sungkyunkwan University School of Medicine, Seoul, South Korea (who was not involved with the study) noted that, "Without ethnic or genetic ancestry data, the study cannot distinguish whether observed regional differences reflect genetic predisposition, environmental exposures, health-care disparities, or combinations thereof…Despite these limitations, this study provides a necessary foundation for global health planning…With appropriate refinements, particularly ethnic and genetic ancestry stratification that acknowledges the distinctive molecular signatures of African, Asian, and other ethnic and genetic ancestry populations, this study can achieve its goal of informing evidence-based cancer control strategies worldwide."