Abstract B125: Use of ambulatory surgery centers for breast cancer surgery is associated with better survival: A population-based assessment in California

Abstract Background: Ambulatory surgery centers (ASCs) offer patients the convenience of having surgeries and procedures performed safely outside the hospital setting. Use of ASCs has gained growing popularity since its inception in 1970 due to high quality service, patient-centered care, reduced costs, and patient satisfaction. Breast cancer is the most common cancer among women and generally treated with surgery. Increasing volumes of breast cancer surgeries now happen in ASCs. Although there were reports of favorable outcomes following breast cancer surgery in ASCs, population-based assessment has been lacking. Our objective was to provide a population-based assessment of survival differences between breast cancer patients treated in ASCs and those treated in inpatient settings. Methods: We used the linked dataset between the cancer incidence and survival data collected by the California Cancer Registry (CCR) and the patient-level service utilization data from hospitals and healthcare facilities collected by the California Office of Statewide Health Planning and Development (OSHPD) records. We identified 191,400 adult women (>=18 years of age) diagnosed with first primary breast cancer during 2005-2019 with known disease stage in the CCR data, who also had first breast cancer related surgery records within 2 months before and 12 months after the cancer diagnosis during 2005-2020 in the OSHPD data. We compared the 5-year observed survival by cancer stage (localized, regional, or distant), surgery type (lumpectomy or mastectomy), and surgery setting (inpatient or ASC). Cox proportional hazards model was used to calculate the hazard ratios (HRs) of death probabilities by surgery setting, stratified by surgery type, while controlling for confounders of age, race/ethnicity, socioeconomic status, stage, and Charlson comorbidity score. Results: The proportion of surgery done in ASCs, as opposed to inpatients, was 96% among the localized-lumpectomy patients, 89% regional-lumpectomy, and 80% distant-lumpectomy. Use of ASCs is substantially lower among mastectomy patients across stage: 45% among the localized-mastectomy patients, 40% regional-mastectomy, and 36% distant-mastectomy. The 5-year survival is consistently higher for ASCs than inpatients regardless of stage and surgery type. According to the multivariable HRs, survival for ASC group was 25% higher than the inpatient group for lumpectomy and 12% higher for the mastectomy group (p<0.0001 for both). However, non-Hispanic black and low SES women respectively experienced excessive mortality in the multivariate analysis regardless of surgery type. Conclusion: The better survival outcomes associated with use of ASCs are reassuring. But more work needs to be done to address the racial and socioeconomic disparities in breast cancer treatment outcomes. Citation Format: Lihua Liu, Juanjuan Zhang, Kathy Wojcik, Irene Kang, Mary Falcone, Caryn Lerman. Use of ambulatory surgery centers for breast cancer surgery is associated with better survival: A population-based assessment in California [abstract]. In: Proceedings of the 15th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2022 Sep 16-19; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2022;31(1 Suppl):Abstract nr B125.