Global Burden of Breast Cancer Among AYAs

In 2021, the global burden of breast cancer among AYAs was notable, with 180,791.49 (95% UI: 166,125.47–197,396.04) new cases and 42,055.42 (95% UI: 38,187.76–46,379.31) deaths reported, and accounted for 2,484,705.41 (95% UI: 2,241,610–2,742,178.83) DALYs (Table 1, Tables S1-S2). The ASIR of female AYAs with breast cancer increased to 11.73/100,000 (95% CI 10.77–12.82) in 2021, with an EAPC of ASIR was 0.83 (95% CI 0.72–0.94) from 1990 to 2021. Meanwhile, the ASMR, ASDR, and age-standardized YLLs rate among female AYAs with breast cancer showed a stable trend; however, the age-standardized YLDs rate showed an increasing trend (EAPC: 0.82, 95% CI 0.71–0.92). Notably, all the ASRs, of male AYAs breast cancer were on the rise globally from 1990 to 2021 (Tables S1 and S3).

Table 1 Breast cancer incidence cases, age-standardized incidence rate, and temporal trends among adolescents and young adults globally and geographic regions in 1990 and 2021SDI Level Burden of Breast Cancer Among AYAs

As for different SDI quintiles, the incident cases among AYAs breast cancer increased from 1990 to 2021, with low-middle SDI quintiles experiencing the most significant upward trend in ASIR (EAPC: 2.24, 95% CI 2.18–2.31). Moreover, the high SDI quintiles had the highest ASIR of female AYAs with breast cancer (17.16/100,000, 95% CI 16.29–18.06), demonstrating a decreasing trend from 1990 to 2021 (EAPC: − 0.12, 95% CI − 0.22 to − 0.02). However, the ASIR of breast cancer in male AYAs exhibited an upward trend in all quintiles (Table 1). From 1990 to 2021, the low-middle and low SDI quintiles exhibited an increasing trend in the ASMR and ASDR of female AYAs with breast cancer. However, except for high SDI quintiles, the ASMR and ASDR of male AYAs showed an upward trend in other SDI quintiles (Tables S1 and S3).

Regional Burden of Breast Cancer Among AYAs

Among the 21 regions, East Asia and South Asia recorded the highest number of incident cases, deaths, DALYs among AYAs with breast cancer in 2021. Notably, The ASRs in North Africa and the Middle East, as well as South Asia exhibited the most significant upward trend (Table 1, Tables S1–S2).

In terms of ASIR among female AYAs, the highest was in high-income North America (19.39/100,000, 95% CI 18.10–20.78). Oceania exhibited the highest ASMR (5.38/100,000, 95% CI 3.60–7.82) and ASDR (311.39/100,000, 95% CI 208.16–453.91) in 2021. However, for male AYAs with breast cancer, Eastern Sub-Saharan Africa ranked first in ASMR (0.18/100,000, 95% CI 0.10–0.33) and ASDR (10.15/100,000, 95% CI 6.07–18.92). From 1990 to 2021, the most significant increase in ASIR (EAPC: 3.33, 95% CI 3.20–3.46), ASMR (EAPC: 1.36, 95% CI 1.22–1.49), and ASDR (EAPC: 1.48, 95% CI 1.35–1.62) among female AYAs were observed in North Africa and Middle East. Nevertheless, East Asia exhibited the most significant upward trends in ASIR and ASDR among male AYAs (Tables S1 and S3).

National Burden of Breast Cancer Among AYAs

In 2021, China and India reported the highest incident cases, deaths, DALYs, YLDs, and YLLs for AYAs breast cancer (Tables S4–S6). The highest ASIR was identified in the Monaco (26.66/100,000, 95% CI 15.36–42.04). From 1990 to 2021, the ASIR increased the most in the Zimbabwe (EAPC: 3.82, 95% CI 2.94–4.71; Table S4 and Fig. 1A). Tokelau had the highest ASMR in 2021, while Zimbabwe showed the most significant upward trend (EAPC: 4.09, 95% CI 3.19–5.00) between 1990 and 2021 (Table S5 and Fig. 1B). As for DALYs, the highest ASDR was observed in the Tokelau (280.76/100,000, 95% CI 178.12–414.27), while the highest increasing trend was observed in the Zimbabwe (EAPC: 4.08, 95% CI 3.18–4.99) from 1990 to 2021 (Table S7 and Fig. 1C).

Fig. 1

The EAPCs of age-standardized rates of breast cancer in adolescents and young adults between 1990 and 2021 at the national level. A Age-standardized incidence rate, B Age-standardized mortality rate, and C Age-standardized DALYs rate. DALYs disability-adjusted life years, EAPCs estimated annual percentage changes

Decomposition Analysis of Breast Cancer Disease Burden Among AYAs Globally

From 1990 to 2021, there was a significant total variation in DALYs among breast cancer in AYAs globally (913,994.98), the growth in DALYs worldwide can be largely attributed to population growth (66.55%) and aging (25.92%; Fig. 2).

Fig. 2

Changes in breast cancer DALYs according to population-level determinants of population growth, aging, and epidemiological change from 1990 to 2021 across location. DALYs disability-adjusted life years, SDI socio-demographic index

Several GBD regions exhibited a decrease in the total variation of DAYLs, but they showed a noticeable increase in epidemiologic changes, including Central Asia (1066.74%), East Asia (241.47%), and Australasia (234.71%). Population growth was the largest contributor to DALYs changes in most regions. South Asia and Southeast Asia exhibited a significant total variation in DALYs, with population growth contributing 54.38% and 50.45% to the change, respectively. In addition, population growth contributed the most to the growth in East Asia (178.24%), population ageing had a considerable contribution to the increased DALYs in Southern Latin America (103.86%) (Table S8 and Fig. 2).

Frontier Analysis of the Burden of Breast Cancer Among AYAs

We conducted a frontier analysis on the basis of ASDR and SDI to better understand the potential improvement in breast cancer disease burden among AYAs on the basis of SDI of each country (Fig. 3A and B). Among female AYAs, the top ten countries with the highest effective difference in breast cancer were Tokelau, Palau, Niue, Zambia, Nauru, American Samoa, Bahamas, Fiji, Kiribati, and Marshall Islands. Conversely, the five countries with the lowest ASDR and minimal effective differences were Somalia, Niger, Chad, Gambia, and Yemen, all of which have SDI of less than 0.5. In contrast, the five countries with high SDI (> 0.85) and relatively high effective difference for their level of development, namely UK, USA, Germany, the Netherlands, and Monaco (Fig. 3C). For male AYAs with breast cancer, we observed that the effective difference tended to decrease as the SDI increased. The top ten countries with the highest effective difference, considering their stage of development, were Zambia, Mozambique, Uganda, Malawi, Eritrea, South Sudan, United Republic of Tanzania, Rwanda, Kenya, and Djibouti (Fig. 3D).

Fig. 3

Frontier analysis for identifying improvement gaps for the burden of AYAs breast cancer. The analysis was based on the SDI and ASDR of AYAs breast cancer from 1990 to 2021. A Male and B Female in 2021. C Male and D Female. The frontier is delineated in solid black color; countries and territories are represented as dots. The top 15 countries with the largest effective difference (largest breast cancer DALYs gap from the frontier) are labeled in black; examples of frontier countries with low SDI (< 0.5) and low effective difference are labeled in blue, and examples of countries and territories with high SDI (> 0.85) and relatively high effective difference for their level of development are labeled in red. Red dots indicate an increase in ASDR in breast cancer from 1990 to 2021; blue dots indicate a decrease in ASDR in breast cancer between 1990 and 2021. AYAs adolescents and young adults, DALYs disability-adjusted life years, SDI socio-demographic index, ASDR age-standardized DALYs rates

Global AYAs Breast Cancer Projections for 2044

According to the forecast data, there will be 244,018 incident cases (238,829 females and 2444 males) of breast cancer globally in 2044 (Fig. 4). We observed increasing incident cases in 16 regions from 2021 to 2044, South Asia was projected the region with the fastest-growing (incident cases: 32,711 in 2021 versus 48,318 in 2044). Meanwhile, South Asia (48,318) and Oceania (567) were expected to the highest and lowest incident cases in 2044, respectively. Subsequently, we also projected deaths rising to 54,202 in 2044. By 2044, it is projected that the global DALYs for breast cancer will reach 3,224,966, marking a 29.79% increase compared with 2021. A large increase will be seen in Eastern Sub-Saharan Africa (DALYs: 184,212 in 2021 versus 453,616 in 2044; Table S9).

Fig. 4

The forecast of AYAs breast cancer to 2044 globally. A Incident cases, B Deaths, and C DALYs. AYAs adolescents and young adults, DALYs disability-adjusted life years