Background: Early-onset cancers (diagnosed before age 50) are an emerging public health concern worldwide. Among women, the cancer burden stems largely from women-specific cancers. Cancers occurring at younger ages often lead to premature mortality with many social consequences due to women’s essential roles in their families. Early-onset cancers' burden has been increasingly studied in high-income countries. However, their patterns remain poorly characterized in low- and middle-income countries (LMICs), such as Mexico, where access to timely cancer diagnosis and care remains challenging. Understanding epidemiologic patterns of early-onset cancers in women may provide critical insights to support early diagnosis interventions, guide resource allocation, and support etiologic research in this vulnerable population
 
Objective: To examine mortality trends in early-onset breast, endometrial, and ovarian cancers among Mexican women by cancer type and birth cohort.
Methods: We obtained breast (ICD-10 code C50), ovarian (C56), and endometrial (C54; C55 corrected) cancer deaths between 1998 and 2024 from Mexico’s National Institute of Statistics and Geography data. EOC deaths were defined as those occurring at <40 years of age for breast cancer and <50 years for ovarian and endometrial cancers. Population estimates from the National Population Council were used to calculate mortality rates by cancer type. Age-standardized mortality rates (ASMRs, Segi World Population) were estimated for 2020–2024. Overall, early- and late-onset and age-specific mortality trends were assessed by estimating the average annual percent change (AAPC) using Joinpoint regression models for the complete period. Age–period–cohort models were additionally fitted to evaluate period and birth cohort effects.
Results: Over the study period, breast (n=151,093), ovarian (n=55,477), and endometrial (n=16,400) cancers accounted for 22.0% of all cancer deaths among women; ASMRs were 10.3 (95% CI: 10.2–10.4), 4.0 (95% CI: 4.0–4.1), and 1.5 (95% CI: 1.5–1.6) per 100,000, respectively. Mortality from all three cancers increased between 1998 and 2024, regardless of age, with AAPCs of 2.3% (95% CI: 2.2–2.4), 2.9% (95% CI: 2.7–3.2), and 5.5% (95% CI: 5.0–6.2), respectively. Early-onset breast cancer mortality did not appear to increase, while early-onset ovarian and endometrial cancers increased at 2.0% (95% CI: 1.7–2.4) and 5.0% (95% CI: 3.9–6.6) in the same period. The highest ovarian and endometrial mortality AAPCs occurred in women aged 44-49 years: 1.8% (95% CI: 1.2–2.3) and 5.9% (95% CI: 4.8–7.5). Women born in 1990 were 1.6 times (95% CI: 1.4–1.8) more likely to die of ovarian cancer and 9.9 times (95% CI: 7.1–13.7) more likely to die of endometrial cancer relative to women born in 1950. Women born in 1995 were 1.2 times (95% CI: 1.0–1.3) more likely to die of breast cancer, compared to women born in 1950.
Conclusions: Early-onset cancer mortality remains low in Mexican women, yet mortality for early-onset ovarian and endometrial cancer is steadily rising. Women born in the 1990s faced a higher cancer mortality relative to those born in 1950. Mexico will need to strengthen early cancer diagnosis in women under 50 and strengthen etiologic research efforts on early-onset cancers.