Year of Publication

2019

College

Public Health

Degree Name

Master of Public Health (M.P.H.)

Committee Chair

Dr. Steve Fleming

Committee Member

Dr. Robin Vanderpool

Committee Member

Dr. Jaclyn McDowell

Abstract

Background and objectives

Breast cancer is one of the most common malignancies among women in the United States. Women residing in the state of Kentucky have breast cancer incidence and mortality rates greater than the national average. Recent studies suggest an association between breast cancer subtypes/hormone receptor (HR) status and the risk of recurrence and the onset of subsequent primary cancer, however, limited research has focused on Kentucky or its Appalachian region.

Investigating these associations may potentially save lives by providing information that can be used in breast cancer education in Kentucky, assessing the population at greater risk of recurrence and subsequent cancer (by subtypes), increasing screening in the population at risk, and developing tailored interventions for each region. Therefore, the purpose of this study was to examine the relationship between breast cancer subtypes/hormone receptor status and the risk of recurrence and/or the risk of subsequent cancers among women in Kentucky with a specific focus on disparities in these risks that may exist between women living in Appalachia compared to non-Appalachia.

Methods

The analysis used data from the Kentucky Cancer Registry (KCR), specifically females ages 18 or older diagnosed with primary breast cancer between 2004 and 2016. A retrospective cohort study was conducted to assess the risk of (1) subsequent primaries and (2) recurrence among each breast cancer subtype/HR status. Subjects’ maximum follow-up period for the cohort study

was five years or 60 months. To assess the relationship between breast cancer subtypes and the risk of recurrence and/or the risk of subsequent cancers, a series of Cox regression analyses were performed. The study was conducted in two parts: first, we analyzed data from women diagnosed between 2004 and 2016, examining HR status as a risk factor and second, we focused on women diagnosed between 2011 and 2016, examining breast cancer subtype as a risk factor.

Results

Between 2004 and 2016, it was observed that women with estrogen receptor-positive (ER+ only) breast cancer had a lower risk of subsequent primaries compared to women with HR+ (estrogen receptor-positive [ER+] and progesterone receptor-positive [PR+]) breast cancer (HR:0.85, 95% CI: 0.74,0.96). When stratified by Appalachian status, a similar trend was only seen among non- Appalachian women (HR:0.80, 95% CI: 0.69,0.94). In examining recurrence outcomes, women with ER+, PR+, and HR-negative (HR-) breast cancer had an increased risk compared to women with HR+ breast cancer with hazard ratios of 1.61 (1.28, 2.03), 2.09 (1.57,3.96), and 3.16 (2.64, 3.79), respectively. Clinically significant disparities in the risk of recurrence between Appalachian and non-Appalachian women were also observed for ER+ (1.49 vs. 1.84), PR+ (2.47 vs 2.30), and HR- (2.07 vs. 2.58) breast cancer subtypes. For the focused analysis (2011- 2016), women with Luminal A and B subtypes had a lower risk of recurrence compared to human epidermal growth factor receptor 2 (HER2) enriched and triple negative in both the

overall and stratified analyses. Also, non-Appalachian women with Luminal B had a reduced risk of subsequent cancers (HR:0.76, 95% CI: 0.59,0.99) compared to non-Appalachian women. Conclusion

Among this population-based sample of women in Kentucky, breast cancer subtype/HR status was associated with the risk of subsequent primaries and recurrence. There were also noted disparities in the risk of recurrence between women who live in Appalachian Kentucky and women living in non-Appalachia. Women living in Appalachian Kentucky tended to have lower risk of recurrence compared to women living in non-Appalachia for similar subtypes adjusted for several clinical, behavioral, and insurance-related variables.

Available for download on Saturday, July 25, 2020

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