Abstract A126: Differential survival among Medicare beneficiaries diagnosed with breast cancer in California
Authors: Liu Lihua Liu , Yan Ying , Kim Sue E. 
Published: December 2023

Abstract
This study examines the differences in breast cancer survival among Medicare beneficiaries enrolled in either Traditional Medicare (TM) or Medicare Advantage (MA) plans during 1999-2017 in California. Medicare is federal health insurance for people of age 65 or older. Beneficiaries can choose between TM (directly administered by the Federal government) or MA (offered by private companies) plans. California (CA) has the largest number of Medicare beneficiaries of any state (6.6 million), nearly half (49%) of them enrolled in MA plans. Due to different management mechanisms, detailed claims data are not routinely submitted and available for MA enrollees as for TM, making objective assessment for the claimed MA advantages and effectiveness hard to find. Medicare beneficiaries often find it challenging to choose between TM and MA during the Medicare open enrollment period or make changes between these two types of plans. The National Cancer Institute’s (NCI) Surveillance, Epidemiology, and End Results (SEER) Program, routinely link its cancer registry data with Medicare to provide detailed information about Medicare beneficiaries aged 65 and older diagnosed with cancer. Using the SEER-Medicare linked data for the state of California (CA), we were able to compare the survival differences among Medicare beneficiaries with female breast cancer (BC) stratified by TM or MA enrollment in CA during 1999-2017. We identified a total of 189,517 women Medicare beneficiaries who had BC, of which 83,223 (43.9%) enrolled in TM and never had MA, while 106,294 (56.1%) ever enrolled in MA regardless of the length of MA coverage. Because Medicare enrollment is on monthly basis and enrollees may change plans during the annual open enrollment period each year. Therefore, among the MA enrollees, we found 61,006 (57.4%) who switched between MA and TM from time to time (MA switch), in contrast to 45,288 (42.6%) who were in MA for the entire study period (MA only). We calculated 5-year observed survival rates from all causes of death among these Medicare beneficiaries with BC, using Kaplan-Meier method. We found that MA switch group had the highest 5-year survival of 81.5% (95% CI: 81.2%-81.8%), followed by MA only (72.6%, 95% CI: 72.1%-73.0%) and TM (72.5%, 95% CI: 72.2%-72.8%) groups. The survival advantage of the MA switch group is evident across race/ethnicity. Asian MA switchers had the highest 5-year survival rate (87.3%) followed by Hispanic (83.3%), Non-Hispanic White (80.5%), and Non-Hispanic Black (75.9%). In a multivariate Cox proportional hazards regression analysis, controlling for sociodemographic and clinical characteristics (i.e., age at diagnosis, race and ethnicity, poverty indicator, summary stage of tumor, marital status, urbanization, and number of cancers), MA switch group displayed a statistically significant (α&lt;0.05) mortality reduction of 25% as compared to the TM group. No significant differences between TM and MA only group was found. More informed and proactive Medicare beneficiaries are associated with the best health outcomes.
Citation Format: Lihua Liu Liu, Ying Yan, Sue E. Kim. Differential survival among Medicare beneficiaries diagnosed with breast cancer in California [abstract]. In: Proceedings of the 16th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2023 Sep 29-Oct 2;Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2023;32(12 Suppl):Abstract nr A126.