Background: Breast cancer (BC) in young women is characterized by an unfavorable prognosis in hormone receptor-positive/HER2-negative tumors, which may be explained by low rates of tamoxifen adherence. In Mexico, up to 14% of all BC diagnoses occur in young women and no data on tamoxifen adherence has been reported. Objective: To estimate the rate of adherence to adjuvant tamoxifen in Mexican young women with BC (YWBC). Methods: A cross-sectional survey was conducted at the National Cancer Institute in Mexico City, among YWBC (≤ 40 years at diagnosis) receiving adjuvant tamoxifen. Adherence was measured subjectively, through self-reported surveys, and objectively, through medication possession ratio (MPR). Descriptive statistics were used to analyze sociodemographic characteristics. To compare associations between patients’ characteristics and adherence, Chi-square test was used for categorical variables and Student’s t-test or Mann–Whitney U-test for quantitative variables. Results: A total of 141 YWBC receiving adjuvant tamoxifen were included. Regarding subjective adherence, 95% expressed taking tamoxifen regularly, 70% reported missing 0 doses in the past 30 days, and 71.6% reported having adverse effects. Regarding objective adherence, 74.8% of patients had an MPR ≥ 80%. The association between subjective and objective adherence was statistically significant (p = 0.004). Subjective adherence was associated with not skipping tamoxifen doses when feeling worse. Objective adherence was associated with having a stable job, not skipping tamoxifen doses when feeling worse, taking additional medications, and time on tamoxifen treatment. Fifty-six percent considered the information on tamoxifen to be insufficient and 37% not understandable. Conclusion: In our study, high subjective and objective adherence rates to adjuvant tamoxifen were reported, although an important proportion of women reported high rates of adverse effects and not fully understanding the benefits of tamoxifen. Strategies to increase tamoxifen adherence may be even more important now that longer durations of treatment or further ovarian function suppression have become the standard of care in YWBC.

Objective: To compare the sociodemographic, diagnostic, clinical, and treatment-related characteristics and outcomes of patients with breast cancer in two hospitals in Mexico according to type of healthcare coverage. Methods: A retrospective cohort study of women with breast cancer according to public or private healthcare coverage in two hospitals was done. Patients were treated by the same group of physicians and healthcare infrastructure. Groups were compared using the chi-square test for categorical variables, Mann–Whitney U-test and Student’s t-test for quantitative variables, and Kaplan–Meier estimator and log-rank test for time dependent outcomes (including recurrence-free and overall survival). A value of p < 0.05 was considered statistically significant. Results: A total of 282 women were included. Mean age at diagnosis was 52 years. Women with public healthcare coverage were diagnosed more frequently with self-detected tumors (82.8% vs 47.9%, p < 0.001) and advanced clinical stage (III and IV) (31.1% vs 17.8%, p = 0.014). More women with public healthcare insurance underwent initial systemic treatment (41.1% vs 17.8%, p < 0.001) and mastectomy (70.1% vs 54.9%, p = 0.020), and received more chemotherapy (79.4% vs 43.8%, p < 0.001) and adjuvant radiotherapy (68.9% vs 53.4%, p = 0.017). Overall, no differences were found in survival outcomes according to healthcare coverage. Trends suggesting worse recurrence-free and overall survival were observed in patients with public coverage at 3 years follow-up in stage III (85.7% vs 67.3% and 100% vs 84.6%, respectively) and triple negative disease (83.3% vs 74.5% and 100% vs 74.1%, respectively). Conclusion: Strategies to promote preventive medicine, diagnostic mammograms, and prompt diagnosis of breast cancer in Mexican women with public health coverage are needed. Access to the main treatment modalities by Seguro Popular and good quality care by an experienced group of physicians likely explains the similar outcomes between patients with private and public healthcare coverage. However, trends suggesting worse survival for patients with public medical coverage with stage III and triple-negative disease should encourage close follow-up.