Dissertation
Rural-urban differences in the management of early-stage breast cancer
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2021
DOI: 10.17077/etd.006318
Abstract
Rural residents diagnosed with cancer often encounter disproportionate barriers in accessing healthcare due in part to increased travel burden, lack of health insurance, and shortages of medical oncologists and related cancer specialists. Such issues related to access can result in the receipt of sub-optimal treatments, including reduced likelihood of finishing treatments, and poorer health outcomes, including higher mortality rates and diminished health-related quality of life. To better understand the impact of rurality on the management of early-stage breast cancers, this dissertation aimed to: (1) describe locoregional treatment trends, including cancer-directed surgery and post-operative radiation therapy (PORT) use, and examine rural-urban differences in surgical choice and use of PORT among women diagnosed with ductal carcinoma in situ (DCIS), (2) describe trends in axillary management, including sentinel lymph node biopsy and axillary lymph node dissection, and examine rural-urban differences in the use and type of lymph node surgery performed with mastectomy among women diagnosed with DCIS, and (3) describe trends in the use of gene expression profiling (GEP) testing for early-stage, invasive breast cancer, examine rural-urban differences in the use of GEP testing, and evaluate the association between GEP test results and receipt of adjuvant chemotherapy. We examined rural-urban differences in locoregional treatment using data from the Surveillance, Epidemiology, and End Results (SEER) Program Patterns of Care (POC) studies. We included all women aged 20 years and older, diagnosed with histologically confirmed DCIS who underwent cancer-directed surgery during the following POC study years: 1991, 1995, 2000, 2005, 2010, and 2015. Of the 3,337 patients who met inclusion criteria, 27% underwent mastectomy, 26% underwent breast-conserving surgery (BCS) without PORT, and 47% underwent BCS with PORT. We found that after adjustment for other covariates, there was no difference in the likelihood of receiving mastectomy between rural and urban patients (adjusted odds ratio (aOR)=0.65; 95% confidence interval (CI) 0.37-1.14). However, rural patients were more likely than urban patients to have mastectomy during 1991/1995 (aOR=1.78; 95% CI 1.09-2.91; pinteraction=0.022), but not thereafter. Across all diagnosis years, rural patients were less likely to receive PORT following BCS compared to urban patients (aOR=0.35; 95% CI 0.18-0.67).
Next, we examined rural-urban differences in the use and type of lymph node surgery performed with mastectomy using data from the 2000, 2005, 2010, and 2015 SEER POC studies. Of the 504 DCIS patients included in the analyses, approximately 81% underwent lymph node surgery at the time of mastectomy. After adjustment of covariates, we found that while lymph node procedures increased over time (p<0.0001), rural patients were less likely to undergo lymph node surgery compared to urban patients (aOR 0.19; 95% CI 0.06-0.66). However, the likelihood of undergoing more aggressive axillary lymph node dissection relative to sentinel lymph node biopsy was lower among rural patients compared to urban patients (aOR=0.16; 95% CI 0.03-0.73). Finally, we examined the association between hospital rurality and GEP testing using data from the Iowa Cancer Registry (ICR). Rural-urban commuting area (RUCA) codes were used to categorize the location of each patient’s surgical hospital into urban (N=43), large rural (N=16) and small rural (N=48) areas. Of 6,726 patients eligible for GEP use, 46% (N=3,069) underwent testing between 2010 and 2018. While overall GEP testing rates increased over time from 42% between 2010-2012 to 51% between 2016-2018 (ptrend<0.0001), use of GEP tests was lowest among patients treated at hospitals located in small rural areas. The odds of GEP testing remained significantly lower among patients treated at hospitals located in small rural areas (aOR 0.55; 95% CI 0.43-0.71), after adjusting for demographic and clinical characteristics. Oncotype Dx (ODX) testing accounted for 95% of all GEP testing in our study population. ODX recurrence score was highly correlated with chemotherapy use across all strata of hospital rurality.
Overall, the findings from each study highlight the importance of rurality and its impact on breast cancer management. As cancer therapies continue to evolve and become more personalized though the use of novel technologies, such as GEP tests, large, population-based studies are needed to better understand the drivers of treatment disparities and how these disparities influence patient outcomes and quality of life. In addition, targeted interventions are needed to increase timely adherence to evidence-based, national clinical practice guidelines, which are intended to optimize patient care.
Details
- Title: Subtitle
- Rural-urban differences in the management of early-stage breast cancer
- Creators
- Danielle J. Riley
- Contributors
- Charles F Lynch (Advisor)Elizabeth A Chrischilles (Committee Member)Mary Charlton (Committee Member)Brian J Smith (Committee Member)Ingrid M Lizarraga (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Epidemiology
- Date degree season
- Autumn 2021
- DOI
- 10.17077/etd.006318
- Publisher
- University of Iowa
- Number of pages
- xvii, 133 pages
- Copyright
- Copyright 2021 Danielle J. Riley
- Language
- English
- Description illustrations
- illustrations (some color), color maps
- Description bibliographic
- Includes bibliographical references (pages 101-133).
- Public Abstract (ETD)
Cancer patients living in rural areas often face challenges in accessing healthcare due to issues related to transportation, lack of health insurance, and shortages of oncologists. These barriers can lead to the receipt of sub-optimal management and poorer health outcomes.
In aim one, 27% of patients with ductal carcinoma in situ (DCIS) received mastectomy, 47% received lumpectomy with radiation, and 26% received lumpectomy without radiation. Compared to patients living in urban areas, we found rural patients were less likely to receive radiation therapy following lumpectomy and, during 1991/1995 only, more likely to receive mastectomy than lumpectomy.
In aim two, nearly 81% of DCIS patients treated with mastectomy received lymph node surgery. We found rural patients were less likely to receive any type of lymph node surgery compared to urban patients. However, of those who received lymph node surgery, rural patients were less likely to receive more aggressive axillary lymph node dissection than sentinel lymph node biopsy.
In aim three, less than half of eligible breast cancer patients received genomic testing. We found patients treated at hospitals in small rural areas, were less likely to receive testing than patients treated at urban hospitals. Of those who received Oncotype Dx testing, results were highly correlated with chemotherapy use.
Overall, the findings from each aim highlight the importance of rurality and its influence on treatment decisions. More studies are needed to better understand how rurality affects treatment choices and to develop interventions to increase timely adherence to national clinical practice guidelines.
- Academic Unit
- Epidemiology
- Record Identifier
- 9984210641302771
Metrics
4 File views/ downloads
132 Record Views