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Explaining Variation in Clinical Practice: Surgical Treatment of Early Stage Breast Cancer Open Access


Other title
breast cancer
Type of item
Degree grantor
University of Alberta
Author or creator
Fisher, Stacey L
Supervisor and department
Yasui, Yutaka (Public Health Sciences)
Winget, Marcy (Public Health Sciences)
Examining committee member and department
Winget, Marcy (Public Health Sciences)
Yasui, Yutaka (Public Health Sciences)
Voaklander, Don (Public Health Sciences)
Dabbs, Kelly (Surgery)
Department of Public Health Sciences
Date accepted
Graduation date
Master of Science
Degree level
Background: Breast conserving surgery (BCS) followed by radiation is the preferred treatment option for early stage breast cancer because it is less invasive than the alternative treatment, mastectomy, and provides a better cosmetic outcome and a superior quality of life. Positive surgical margins after breast conserving surgery (BCS), however, necessitate re-excision surgery by further BCS or by mastectomy. Re-excision is associated with greater morbidity, patient anxiety, poor cosmetic outcome, delayed initiation of adjuvant therapies, and increased medical cost. Objectives: The primary objectives of this research were to: 1) investigate the relationships between clinical, patient, provider and geographic factors and surgery type received; 2) investigate the relationships between clinical, patient, provider and geographic factors and receipt of re-excision surgery; 3) quantify residual surgeon and hospital-specific variation associated with surgery type received and receipt of re-excision and; 4) investigate if re-excision is associated with all cause and breast cancer-specific mortality among patients who receive re-excision, compared to those who receive BCS without re-excision and those who receive an initial mastectomy. Methods: All women diagnosed with stage I-III breast cancer in Alberta from 2002 to 2010 were identified from the Alberta Cancer Registry; demographic, clinical and treatment information was obtained from this source. Alberta Health Physician Claims data were used to identify the type of first breast cancer surgery after diagnosis, subsequent re-excisions within 1 year of initial surgery, and anonymized physician identifiers associated with each procedure. Multilevel logistic regression with surgeons and hospitals as crossed random effects were used to estimate the adjusted odds ratios of mastectomy and of re-excision by the factors of interest. Poisson regression models were fitted to compare all-cause and breast cancer-specific mortality by surgery pattern. Results: Mastectomy was received by 51% of patients and was found to be inversely related to surgeon volume among stage I and II patients. Odds ratios of mastectomy varied widely by individual surgeon and by hospital beyond the variation explained by the factors investigated. Re-excision surgery was received by 19% of patients who initially received BCS. Increasing patient age was associated with re-excision and the odds of re-excision varied significantly through the province. BCS followed by re-excision was not associated with greater all-cause or breast cancer-specific mortality compared to than those who received BCS without re-excision. Conclusions: Both clinical and health system factors are associated with mastectomy and re-excision among breast cancer patients in Alberta. The significant surgeon-specific variation in the likelihood of BCS, and the geographic and surgeon-specific variation of re-excision is concerning. Further research is necessary to understand the reasons for the observed variation so appropriate interventions can be developed and applied.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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