Breast cancer survival in Mexico between 2007 and 2016 in women without social security: a retrospective cohort study.

Background: Essential indicators of health system performance for breast cancer are lacking in Mexico. We estimated survival and clinical stage distribution for women without social insurance who were treated under a health financing scheme that covered 60% of the Mexican population. Methods: We conducted a retrospective cohort study cross-linking reimbursement claims for 56,847 women treated for breast cancer between 2007 and 2016 to a mortality registry. We estimated overall- and clinical stage-specific survival and breast cancer survival according to patient age, state of residence, marginalization, type of treatment facility, and patient volume of the treatment facility. We also explored the distribution of clinical stage according to age, year of treatment initiation, and state where the woman was treated. We used log-rank tests and estimated 95% CIs to compare differences between patient groups. Findings: Median age was 52 years (interquartile range [IQR] 45, 61) (Sixty five percent patients (36,731/56,847) had advanced disease at treatment initiation. Five-year overall survival was 72.2% (95% CI 71.7, 72.6). For early disease (excluding stage 0), 5-year overall survival was 89.0% (95% CI 88.4, 89.5), for locally advanced disease 69.9% (95% CI 69.0, 70.2) and for metastatic 36.9% (95% CI 35.4, 38.4). Clinical stage at treatment initiation and breast cancer survival remained unchanged in the period analyzed. Clinical stage and survival differed across age groups, state of residence, and type of facility where women received treatment. Interpretation: In the absence of population-based cancer registries, medical claims data may be efficiently leveraged to estimate essential cancer-related performance indicators. Funding: The authors received no financial support for this research.