Purpose: To present the use of administrative databases and registries to confirm and identify incident breast cancer (BC) cases in a prospective cancer cohort in Mexico where cancer registry coverage is limited.

Methods: The Mexican Teacher's Cohort (MTC) was established in 2006-2008 when 115,314 female teachers residing in a 12-state area in Mexico (cancer registry coverage, 13%) responded to a questionnaire on reproductive, lifestyle factors, and medical conditions. We projected 955 BC incident cases by the end of 2019. Study participants reported new BC diagnoses in follow-up questionnaires between 2008 and 2020. Self-reports were confirmed by directly contacting participants. Administrative (one medical claims database, two reimbursement databases, and electronic medical records from two institutions) and population-based cancer registry data were used to confirm previously self-reported BC and identify additional cases. Two independent national mortality registries were used to identify BC deaths (2006-2018).

Results: We have identified 632 self-reported cases and confirmed 300 through participant contact or presence in a database. We additionally identified and confirmed 100 cases from administrative databases, 25 from cancer registries, and 94 from mortality registries. Median age at diagnosis was 49.0 (± SD 6.9), 63.2% (n=538) of the cases were pre-menopausal and 4.8% (n=41) occurred in indigenous women. Thus far, we have identified 89% (n=851) of the projected number of BC cases by the end of 2019 and confirmed 60.8% (n=518). We know the treating hospital for 30.0% (n=255) of the total cases and obtained histopathology reports from 12.0% (n=62) of the confirmed cases.

Conclusion: Leveraging administrative databases for confirmation and identification of incident BC cases is feasible in the MTC. Low- and middle-income countries with limited cancer registry coverage seeking to develop prospective cancer cohorts should explore the use of administrative databases to confirm and identify incident cancer cases.

Citation Format: Liliana Gómez-Flores-Ramos, Marion Brochier, Adrian Cortés-Valencia, Susana Lozano-Esparza, Aura Erazo Valle Solís, Aureliano Plácido Méndez, Olga Rosalinda Rivera Ontiveros, Alberto Cundapí Núñez, Angélica Pon Méndez, Martín Lajous. Confirmation and Identification of Incident Cases of Breast Cancer in a Setting with Limited Cancer Registry Coverage: The Mexican Teachers' Cohort [abstract]. In: Proceedings of the 9th Annual Symposium on Global Cancer Research; Global Cancer Research and Control: Looking Back and Charting a Path Forward; 2021 Mar 10-11. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2021;30(7 Suppl):Abstract nr 82.