Abstract P3-12-30: Impact of medicaid expansion on breast cancer stage at diagnosis: Exploring the mechanisms at play
Authors: Koroukian Siran M. , Dong Weichuan , Albert Jeffrey , Kim Uriel , Rose Johnie , Owusu Cynthia , Zanotti Kristine , Cooper Gregory , Tsui Jennifer 
Published: March 2022

Abstract
Background: Prior studies have shown significant improvements in earlier breast cancer stage at diagnosis following Medicaid expansion. However, the mechanisms behind this finding have not been explored. The timing of Medicaid enrollment among cancer patients has been shown to be associated with cancer stage at diagnosis, with significantly higher percentages of women with late-stage breast cancer enrolling in Medicaid shortly before or after cancer diagnosis (hereafter referred to as the Peri-dx group), compared to those continuously enrolled in Medicaid at least 4 months prior to cancer diagnosis (Pre-dx group). Hence, we conducted a causal mediation study based on a logistic regression model to determine whether the observed improvements in breast cancer stage at diagnosis from Pre- to Post-expansion can be attributed to a decreasing percentage of women in the Peri-dx group, and a corresponding increase in the Pre-dx group. Methods: We used the linked Ohio Cancer Incidence Surveillance System and Medicaid data, and identified women in Ohio age younger than 66 years, diagnosed with incident invasive breast cancer during the period May 2011-December 2017, and enrolled in Medicaid at the time of cancer diagnosis (n=5,880, excluding those with unstaged/unknown-stage cancer). We defined the years 2011-2013 and 2014-2017 as the Pre- and Post-expansion periods, and Month 0 as the month of cancer diagnosis. We identified women enrolled in Medicaid in the -3 to +3-month window in the Peri-dx group, and those continuously enrolled in Medicaid at least 4 months prior to cancer diagnosis in the Pre-dx group. We conducted a causal mediation analysis to estimate the direct, indirect, and total effect of Medicaid expansion on being diagnosed with local-stage disease versus late- (regional- and distant-) stage disease, with the mediator variable being a patient in the Pre-dx group (versus in the Peri-dx group), adjusting for patient- and area-level covariates. Results: The median age of our study population was 53 years; 75.0% were non-Hispanic White. The percent of breast cancer patients diagnosed with late-stage disease was 43.5% and 53.4% in the Pre- and Peri-dx groups, respectively. We observed a clear shift in the distribution of breast cancer patients from the Peri- to the Pre-dx group over time, with an increase in the percentage of women in the Pre-dx group (from 55.2% to 74.2% from the Pre- to Post-Expansion period), and a corresponding decrease in the Peri-dx group (from 44.8% to 25.8%). Findings from our causal mediation analysis, based on a risk difference scale, showed that while the direct effect of Medicaid expansion on being diagnosed with local-stage disease was not significant (coefficient: 0.037, (p=0.297)), both the indirect and total effects were highly significant (0.049 (p &lt; 0.001), and 0.086 (p=0.015)). Conclusion: Our results indicate that the improvements in breast cancer stage at diagnosis from Pre- to Post-Expansion can be attributed to a decrease in the Peri-dx group, and a corresponding increase in the Pre-dx group, which improves access to screening, increases the likelihood of breast cancer patients being engaged with Medicaid providers, and reduces delays in enrollment logistics prior to treatment initiation.
Citation Format: Siran M. Koroukian, Weichuan Dong, Jeffrey Albert, Uriel Kim, Johnie Rose, Cynthia Owusu, Kristine Zanotti, Gregory Cooper, Jennifer Tsui. Impact of medicaid expansion on breast cancer stage at diagnosis: Exploring the mechanisms at play [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-12-30.