Introduction
Breast cancer remains the most common malignancy among women globally, with a rising burden in younger demographics that is increasingly drawing clinical and public health attention. Recent epidemiological evidence from the US and UK has identified a notable increase in early-onset breast cancer (EOBC), typically defined as diagnosis before age 40 or 50, over the past decades. This trend borders on a significant public health issue due to the potential impact on life expectancy and quality of life in younger populations. The present article synthesizes robust national registry data from France spanning 1990 to 2023 to quantify EOBC incidence rates and discusses potential etiological factors and implications.
Study Design and Methods
The French cancer incidence data were derived from the French Network of Cancer Registries (Francim), ensuring high-quality, population-based capture. This resource includes 20 district registries, representing an average surveillance cohort of over five million individuals per annum. From 1985 through 2018, a total of 229,352 breast cancer cases were documented. Incidence estimation employed a Poisson mixed-effects model integrating age and diagnosis year as continuous variables via penalized splines, accounting for departmental random effects. Incidence was directly age-standardized (ASR) using the world standard population. Age-specific incidence trends were analyzed for key ages (30, 40, 50, 60, 70, and 80 years), with projections extended to 2023 excluding COVID-19 pandemic effects. Average annual percentage change (AAPC) quantified temporal trends.
Key Findings
The analysis demonstrates a steady and statistically significant increase in EOBC incidence in French women aged 30 and 40 years, rising from 16.1 (95% CI: 14.7–17.8) to 26.3 (95% CI: 20.7–33.3) per 100,000 person-years at age 30 and from 98.7 (95% CI: 93.8–103.7) to 131.2 (95% CI: 115.8–148.7) per 100,000 person-years at age 40 between 1990 and 2023. The corresponding AAPCs were 1.5% and 0.9%, respectively. This pattern is consistent with trends observed in the total population and other age groups, though the 60-year age group showed a comparatively attenuated increase. Stratified analyses by five-year age bands between 30 and 40 years further confirmed upward incidence trends.
Cross-country comparisons reveal similar EOBC incidence elevations in the US and UK, with the younger cohorts exhibiting faster growth rates than older populations. For example, in the US, the average annual rise was 1.4% for younger women versus 0.7% for older women, while the UK saw a 22% overall increase in incidence among 25–49-year-olds over approximately two decades.
Expert Commentary and Biological Plausibility
Young women are typically not included in routine breast cancer screening programs, suggesting that increasing incidence rates are unlikely artifacts of enhanced detection alone. Instead, concurrent shifts in hormonal and reproductive factors likely play a pivotal role. These include rising age at first childbirth, declining fertility rates, younger menarche, diminished breastfeeding practices, and increased oral contraceptive use—each associated with breast cancer risk modulation, particularly hormone receptor (HR)-positive subtypes.
Supporting this, US data highlight that the EOBC incidence rise predominantly affects estrogen receptor-positive tumors, aligning with French findings of increasing estrogen receptor positivity over time, potentially reflecting hormonal milieu changes. However, limitations exist, as hormone receptor status was not available in the French registry dataset for trend analysis.
Beyond hormonal factors, lifestyle modifications over recent decades—such as changes in diet, increased alcohol consumption, sedentary behavior, urbanization, environmental exposures, and psychosocial stress—may contribute. The possible influence of genetic or epigenetic changes, including de novo germline mutations, somatic mutations, or epigenetic alterations induced by environmental stresses, remains underexplored and warrants investigation.
Implications for Screening and Prevention
The rise in EOBC incidence has prompted reconsiderations of breast cancer screening policies. Notably, the US Preventive Services Task Force and American Cancer Society lowered the recommended starting age for biennial mammography screening from 50 to 40 years in 2024. Contrastingly, European guidelines, including those by the European Commission Initiative on Breast Cancer (ECIBC), currently recommend against routine screening mammography for average-risk women aged 40–44 due to an unfavorable balance of benefits and harms. However, some European programs have lowered the starting invitation age to 45 years. France maintains invitations for biannual mammography screening from age 50 to 74.
Given these divergent recommendations, the growing EOBC incidence underscores an urgent need for nuanced assessment of screening strategies, integrating risk stratification and evaluating harms, benefits, and resource utilization.
Conclusion
Population-based French registry data corroborate a sustained increase in breast cancer incidence among young women over the last three decades, echoing trends in other Western populations. Although changes in hormonal and reproductive factors likely underpin part of this trend, lifestyle, environmental, and genetic contributors must be further elucidated. This evolving epidemiology challenges existing paradigms for breast cancer screening and highlights an imperative for research focused on tailored prevention, early detection, and risk assessment in younger women.
References
Pujol P, Remontet L, Lapôtre-Ledoux B, Rogel A, Lafay L, Molinié F. Increasing incidence of breast cancer in young women over time. Breast. 2025 Oct;83:104555. doi: 10.1016/j.breast.2025.104555. Epub 2025 Aug 5. PMID: 40774220; PMCID: PMC12351116.
