Examination Date

5-30-2023

Degree

Dissertation

Degree Program

Epidemiology

Examination Committee

Xiao-Cheng, MPH; Edward Trapido, PhD; Edward S. Peters, DMD; Tekeda Ferguson, PhD; Mei-ChinHsieh, PhD; Qingzhao Yu, PhD

Abstract

Survival and surgery receipt are key outcome variables for my dissertation research. The three aims of this study are: (1) examine socio-economic status (SES) disparities in survival among HR+/HER2- breast cancer (BC) women and differentiate the mediating effects of the Oncotype DX (ODX) test and stage; (2) compare the long-term survival differences among the surgery choices (mastectomy vs. breast-conserving therapy plus radiation (BCT)); (3) understand how distance to radiation therapy facilities (RTF) matters for older and young breast cancer women in choices of BCT. Data from the Louisiana Tumor Registry and the CDC Pattern of Care (POC) study data were used to accomplish the three aims. Three main findings were found through analytical approaches such as mediation analysis, Cox proportional hazard regression, logistic regression, and interaction assessment.

First, early-stage breast cancer (ESBC), HR+/HER2- women with low socioeconomic status (SES) had a significantly higher risk of dying than women with high SES. ODX testing and tumor stage at diagnosis significantly mediated the association of SES and survival.

Second, ESBC women receiving a mastectomy had significantly higher overall cause of deaths (22%) and BC-specific deaths (26%) than women receiving BCT after adjusting for confounders and covariates, including comorbidity severity, adjuvant treatment (chemotherapy and hormone therapy), and molecular subtype of HR/HER2.

Third, the distance to the nearest or nearest accessible radiation therapy facility (RTF) influences the surgery choice, especially among women aged ≥65 years with ESBC.

In summary, our results found lower survival disparities among ESBC, HR+/HER2- women with a low SES are partially attributed to the mediating effect of ODX testing and tumor stage at diagnosis. Furthermore, even after adjusting for confounding factors such as comorbidity severity, adjuvant treatment, and molecular subtype, ESBC women receiving BCT had better 10-year survival than those who underwent mastectomy. Additionally, the distance to RTF influences the surgery choices, especially among older women. These results have implications for targeted interventions aimed at improving the health outcomes of breast cancer patients. It highlights the importance of ODX testing for eligible patients, promoting the preference for BCT whenever feasible, and addressing transportation obstacles to ensure access to radiation therapy.

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