Date of Graduation

2015

Document Type

Dissertation

Degree Type

PhD

College

School of Pharmacy

Department

Pharmaceutical Sciences

Committee Chair

Suresh S Madhavan

Committee Co-Chair

Hannah W Hazard

Committee Member

Kimberly M Kelly

Committee Member

Dustin M Long

Committee Member

Usha Sambamoorthi

Abstract

Breast cancer (BC) is the 2nd most commonly diagnosed type of cancer in the United States (US) and the 1st among women, with 57% of incident cases in those age > 60 years. Relative to other cancers, BC has high survival rates, with a 89% 5-year overall survival rate. High survival rates are due to improvements in disease understanding, treatment, and earlier stage at diagnosis from increased routine BC screening. Yet, disparities in treatment and survival outcomes persist. Epidemiologic studies suggest that elderly women experience disparities uniquely associated with increasing age and comorbidity, in addition to those associated with socio-demographic characteristics, access to oncology care resources, and clinical prognostic factors. This sequence of retrospective database studies sought to characterize and examine associations with initial loco-regional treatment for stage I and II BC, receipt of guideline-concordant care (GCC) and individual tests and treatments for stage I-III BC, and overall 5-year survival among using the first two study cohorts and a third, more broadly inclusive cohort of elderly women with stage I-III BC. Cohorts of women age ≥ 66 years diagnosed in 2003--2009 were selected from the Surveillance, Epidemiology, and End Results-Medicare (SEER-Medicare) linked dataset. Regarding the 1st study, 55% of women had breast-conserving surgery (BCS) plus radiation therapy (RT), 23% has mastectomy, and 22% had BCS without RT as their initial loco-regional treatment. Compared to women who received BCS plus RT, those who were older, of greater comorbidity, later stage, or non-white race were more likely to have had mastectomy or BCS without RT. Women who were less likely to have had mastectomy or BCS without RT were those treated by an oncology surgeon or both an oncology and general surgeon vs. a general surgeon only, from areas of less education, lower income, or lived in metro areas. Regarding the 2nd study, only 34% received GCC, 61% had RT, and 25% had chemotherapy but, most women had their hormone receptor (HR) statuses and lymph nodes tested. Women who were older, of greater comorbidity, stage II vs. I, lymph node negative, or non-white race were less likely to receive GCC, while those who were HR negative or treated by an oncology surgeon or both an oncology and general surgeon, vs. a general surgeon only were more likely to receive GCC. Regarding the 3rd study, overall 5-year survival ranged from 82%-88% among the three cohorts. The risk of death was greater for women who were older, of greater comorbidity, diagnosed at a later stage, HR negative, treated by mastectomy, BCS without RT, did not received GCC, RT, or chemotherapy, but was lower for women treated by an oncology surgeon or both an oncology and general surgeon vs. a general surgeon only. Despite recommended treatment guidelines, increasing age and comorbidity are strongly associated with less aggressive BC among elderly women. Older women with BC should receive treatment according to guidelines as it would be otherwise given to younger women, health permitting. While the increased risk of death associated with increasing age is inevitable, targeting health behaviors to decrease comorbidity and continued routine BC screening for earlier stage at diagnosis may go a long way to improve survival.

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