Abstract P6-02-02: Increased interval cancers after the 2009 U.S. preventive services task force guidelines: A single-center, retrospective analysis
Authors: Townsend NT , Everhart RM , Bayliss EA , Jaiswal K 
Published: May 2016

Abstract
Background: In late 2009, the U.S. Preventive Services Task Force (USPSTF) increased the recommended time between screening mammography from one year to two years. We examined the effect of USPSTF recommendations in an integrated safety-net system whose patients often have intermittent access to care. The purpose of this study was to determine if changes in screening guidelines were associated with stage migration or changes in rate of interval cancers.
Methods: We conducted a retrospective cohort analysis of breast cancer patients diagnosed between 2005-2013 at one safety-net hospital. We abstracted stage at diagnosis, time intervals between screening and diagnostic imaging, as well as BIRADS classification from clinical and administrative billing data. We divided patients into two cohorts: Those diagnosed with breast cancer "pre-2010" (2005 – 2010) and "post-2010" (2011-2013). We compared stage of diagnosis between cohorts using Chi-Square tests. In a subset of patients for whom we had prior screening imaging information, we determined the rate of interval cancers. Interval cancers were defined as patients whose diagnosis occurred within 14 months (pre-2010) or within 26 months (post-2010) of normal screening mammography. Logistic regression was used to determine the unadjusted odds of interval cancer as a function of being post-2010 versus pre-2010.
Results: There were 521 unique, breast cancer patients between 2005-2013,
Distribution of Breast Cancer by Stage Stage 0Stage IStage IIStage IIIStage IVTotal2005-200941816142242492010-20134679824421272
249 in the 'pre-2010' cohort, and 272 in the 'post-2010' cohort. In the 2005-2009 cohort, 32.5% and 24.5% of patients were stage I and Stage II respectively. In 2010-2013, 29.0% and 30% were stage I and stage II, respectively. The difference in stage at diagnosis was not statistically significant (p=0.62). In a subset of 178 patients with available screening imaging data, we determined the rate of interval cancers. Pre-2010, 7.4% (8/108) of patients had an interval cancer. Post-2010, 20% (14/70) patients had an interval cancer. Patients diagnosed post-2010 had three times the odds of having an interval cancer compared to pre-2010 patients (OR = 3.13, 95% CI 1.24-7.91, p=0.01).
Discussion: The USPSTF 2009 recommendation is associated with a statistically significant increase in interval cancers in a safety-net population, but we cannot conclude that this contributes to stage migration in this limited population. Investigation of larger groups is needed to further assess how USPSTF guidelines affect outcomes in underserved populations.
Citation Format: Townsend NT, Everhart RM, Bayliss EA, Jaiswal K. Increased interval cancers after the 2009 U.S. preventive services task force guidelines: A single-center, retrospective analysis. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-02-02.