According to the World Health Organization (WHO), the global prevalence of cancer is increasing rapidly.1 Breast cancer (BC) is the most common cancer among women, and the incidence rate of BC has increased by 0.5% per year over the past 40 years.2

The pathophysiology of BC is multidimensional and not yet well understood; however, certain risk factors for this disease are known and can be divided into 2 categories: genetic and environmental. Genetic causes, such as mutations in BRCA1 and BRCA2 (tumor suppressor genes), cause approximately 10% of BC cases.3 Other known risk factors include a history of in situ ductal carcinoma, high body mass index (BMI), first birth over age 30 years, early menarche (before age 13 years), family history of breast or ovarian cancer, late menopause, alcohol consumption, and use of postmenopausal hormone therapy.4,5

The increase in the number of cases in recent years is due to the decline in fertility among women owing to the increased use of oral contraceptives6 and increasing BMI and obesity.7 Another important risk factor for BC is alcohol consumption. In 1990, 5.6 L of alcohol was consumed per adult per year, which increased to 6.5 L in 2019 and is expected to reach 7.6 L by 2030. This increase in alcohol consumption may increase BC incidence and mortality.8

Exposure to high levels of endogenous or exogenous estrogen is generally accepted as the most important risk factor for the development of BC. Epidemiologic studies have shown that an increase in serum E1 and E2 levels after menopause significantly increases the risk of BC.9

Breast cancer mortality rates have decreased by 43% since 1989, with an average of 460 000 BC deaths; however, the rate is disproportionately high among women in resource-limited settings. The reason for this decline is early diagnosis through mammography and screening. Despite having a 22% lower incidence than White women, Black women experience 19% more deaths owing to screening and treatment in unreliable centers.2

In summary, changes in BC risk factors can lead to large changes in the number of cases, prevalence, and mortality, and predicting the extent of this disease in the future will better prepare health system planners to deal with its complications. This will give them a general outline to know what resources and how much are needed to better control this disease in the future (e.g., how much chemotherapy, surgery, oncology specialists, and radiotherapy are needed).10,11

Despite extensive knowledge of BC risk factors, less attention has been paid to how the future burden of the disease will evolve across regions with different levels of sociodemographic development. Understanding projected trends and inequalities in incidence, mortality, and disease burden is essential for anticipating health system needs and guiding equitable resource allocation. Therefore, this study aimed to examine trends in BC incidence, mortality, and burden from 1990 to 2021 by age and geographic region, to project these indicators through 2030, and to assess the contribution of demographic and epidemiological factors to observed changes.

In the present study, data from the GBD study were used to examine the global burden of BC from 1990 to 2021 and to project trends from 2022 to 2030, stratified by age and country-level SDI. The primary contribution of this analysis is not etiological explanation, but the projection of future BC burden and the identification of widening inequalities across sociodemographic settings. The results showed that the absolute numbers of BC incidence and deaths increased by approximately 1.4% and 0.8% per year, respectively, from 1990 to 2021.

The increasing absolute number of total cases, alongside decreasing age-standardized mortality rates, highlights a key public health challenge. Although advances in therapy are enhancing individual outcomes, demographic changes are contributing to a growing population requiring medical care. This issue is especially pronounced in middle-SDI regions that are experiencing rapid epidemiological transitions.

This is also true in the study by Zhang et al., who found that the burden of BC in women generally increases with age, with the highest burden in the 45 to 49 years age group.12 In our study, this increasing trend was also observed, with the highest incidence and number of deaths in patients aged 40 to 59 years and 60 years or older.

Better screening and early detection of BC have led to more accurate counts in high-SDI areas; however, the results showed that the number of deaths has increased less in high-SDI areas than in other areas, which may be due to more advanced medical technology, effective preventive measures, and greater health awareness among the population in these areas. This increase is projected to be greater in low- and medium-SDI areas by 2030.13

The pronounced disparities observed across SDI regions are likely driven by structural determinants of health rather than biological differences alone. Limited access to organized screening programs, delayed diagnosis, and inadequate health care infrastructure contribute to higher mortality and DALY burdens in low- and middle-SDI settings. In addition, financial barriers, including out-of-pocket costs and limited insurance coverage, restrict access to timely and effective treatment, while shortages of trained oncology workforce further exacerbate inequalities in BC outcomes.14–16

To mitigate the projected increase in BC burden in low-SDI regions, targeted and context-specific interventions are urgently needed. These include the expansion of cost-effective screening strategies such as mobile mammography and community-based clinical breast examination programs, particularly in underserved and rural areas. Strengthening health care capacity through workforce training, task shifting, and integration of cancer services into primary health care systems may improve early detection and continuity of care. In parallel, subsidized treatment programs and improved financial protection mechanisms are essential to reduce treatment delays and prevent catastrophic health expenditures among vulnerable populations.17–19

The substantial rise in DALYs observed in low- to middle-SDI regions, particularly among women aged 40 to 59 years, likely reflects structural inequalities in health care access and capacity rather than direct environmental or psychosocial influences. Lower-SDI regions frequently face multiple challenges, including limited screening availability, delays in diagnosis, less comprehensive treatment options, and higher rates of modifiable risk factors such as obesity. These systemic barriers often result in later-stage diagnoses and increased disability among survivors, thereby contributing to a higher DALY burden. In contrast, regions with higher SDI benefit from well-established screening programs, earlier detection, and access to advanced multidisciplinary care, which together mitigate disability and mortality. Accordingly, our projection of a continued increase in DALYs through 2030 highlights the pressing need to address these health care disparities at a systemic level.20

The AAPC of deaths increased between 1990 and 2021, with the highest rate in the 60 years or older age group. This increase is also expected to continue in this age group from 2022 to 2030 and to be higher than in other age groups. These findings suggest that the increase in BC prevalence is associated with population aging, as people in this age group are more exposed to genetic changes and environmental factors. As a result, the overall risk of cancer increases with age. The results also showed that the lowest increase in the AAPC of deaths was observed in countries with a high SDI, suggesting that the impact of BC varies according to the SDI of the region.12

The observed increase in age-standardized BC mortality rates in low- and middle-SDI regions represents a critical public health concern. Unlike high-SDI settings, where mortality declines reflect advances in early detection and treatment, many low- and middle-SDI countries continue to face systemic barriers, including limited screening coverage, delayed diagnosis, inadequate referral pathways, and restricted access to effective therapies. These structural constraints contribute to later-stage presentation and poorer survival outcomes, despite rising diagnostic capacity. From a policy perspective, these findings underscore the need for targeted investments in cost-effective screening strategies, strengthening of primary health care systems, expansion of oncology treatment infrastructure, and integration of BC services into universal health coverage frameworks. Addressing these systemic gaps will be essential to reverse unfavorable mortality trends and reduce global inequities in BC outcomes.21–26

The results based on age-standardized BC rates show that the incidence rate is increasing overall, from 40.28 per 100 000 people in 1990 to 46.43 per 100 000 people in 2021, and this trend is projected to increase to 47.97 per 100 000 people in 2030. Interestingly, the incidence rate is decreasing in areas with a high SDI, which may be due to the socioeconomic and health conditions of these areas. In particular, the BC mortality rate has decreased over the years studied, so that the DALY and YLL parameters also show a decreasing trend. This decreasing trend was more pronounced in people 60 years or older and in areas with a high SDI, which may be due to advances in medical technology and treatment methods and changes in public health strategies that affect mortality and the overall burden of the disease.27,28

Therefore, in light of these findings, it is predicted that global disparities in the burden of BC in women will emerge, with some regions experiencing a higher burden owing to limited health resources and preventive measures, and others experiencing a lower burden owing to improved health care, preventive measures, and early detection.12 However, the establishment of the Global BC Initiative in 2021, which emphasizes health promotion, early and rapid detection, and comprehensive treatment of BC, may reduce this global disparity and the incidence of the disease through effective screening programs in the global fight against BC.

This study found a significant association between BC trends in women from 1990 to 2021 and the projected burden from 2022 to 2030. This positive association underscores the potential link between past and future trends and suggests a continuing influence of disease pathogenesis and long-term lifestyle stability,29 genetic factors, environmental factors,30 and socioeconomic conditions.31 These findings highlight the importance of using historical data to predict future trends in order to develop appropriate global strategies for the prevention and treatment of BC in women, taking into account regional disparities and long-term patterns.

Our projections suggest that by 2030, the annual number of new cases requiring management will increase by approximately 457 000 compared with 2021, placing a significant demand on oncology services. In resource-limited settings, emphasis on cost-effective approaches, such as clinical breast examination and the enhancement of referral systems, will be essential. Across all regions, integrating survivorship care to address the growing burden of YLDs should become a core component of cancer control planning. These forecasts provide evidence to guide the strategic priorities of the WHO Global BC Initiative, particularly in efforts to reduce disparities.

This study provides a comprehensive assessment of the global burden of BC among women from 1990 to 2021 and projects future trends through 2030 using a Bayesian modeling framework. While age-standardized mortality and DALY rates are projected to decline, the absolute number of BC cases and deaths is expected to continue increasing worldwide, largely driven by population growth and aging. Substantial disparities persist across SDI regions, with the greatest future increases projected in low- and middle-SDI settings, reflecting structural inequities in screening, diagnosis, and access to effective treatment. These findings underscore the urgent need for targeted, context-specific interventions—particularly in resource-limited regions—to strengthen early detection, expand affordable treatment, and reduce widening inequalities in BC outcomes globally.