Abstract
PURPOSE: Controversy continues regarding the effect of screening mammography on breast cancer outcomes. We evaluated late-stage cancer rate and overall survival (OS) for different screening intervals using a real-world institutional research data mart. METHODS: Patients having both a cancer registry record of new breast cancer diagnosis and prediagnosis screening history between 2004 and 2019 were identified from our institutional research breast data mart. Time interval between the two screening mammograms immediately preceding diagnosis and the time to cancer diagnosis were determined. Screening interval was deemed annual if ≤15 months, biennial if >15 and ≤27 months, intermittent if >27 months, and baseline if only one prediagnosis screen was known. The primary end point was late-stage cancer (TNM stage IIB or worse), and the secondary end point was OS. The association of screening interval and late-stage cancer was analyzed using multivariable logistic regression adjusting for prediagnosis characteristics. Proportional hazards regression was used for survival analysis. Potential lead time was analyzed using survival from a uniform fixed time point. RESULTS: In total, 8,145 patients with breast cancer had prediagnosis screening mammography in the timeframe. The percentage of late-stage cancers diagnosed increased significantly with screening interval with 9%, 14%, and 19% late stages for annual, biennial, and intermittent groups (P < .001), respectively. The trend persisted regardless of age, race, and menopausal status. Biennial and intermittent groups had substantially worse OS than the annual screened group, with relative hazards of 1.42 (95% CI, 1.11 to 1.82) and 2.69 (95% CI, 2.11 to 3.43), respectively, and 1.39 (95% CI, 1.08 to 1.78) and 2.01 (95% CI, 1.58 to 2.55) after adjustment for potential lead time. CONCLUSION: Annual mammographic screening was associated with lower risk of late-stage cancer and better OS across clinical and demographic subgroups. Our study suggests benefit of annual screening for women 40 years and older.