To assess the association between local treatment modality, surgery or radiotherapy, and non-prostate cancer and cardiovascular mortality in patients treated for non-metastatic prostate cancer, given the high competing risk of mortality in this population.
We performed a population-based, retrospective cohort study of men treated for non-metastatic prostate cancer in Ontario, Canada from 2002-2009. Patients treated with surgery and radiotherapy were matched on demographics, comorbidity, and cardiovascular risk factors. The primary outcome was non-prostate cancer mortality. Outcomes were compared using the Fine & Gray sub-distribution method with generalized estimating equations. We used a previously published technique to quantify the prevalence and strength of residual confounding necessary to account for observed results.
We examined 5393 pairs of matched men. The 10-year cumulative incidence of non-prostate cancer mortality was higher among patients who underwent radiotherapy (12%) than surgery (8%; adjusted sub-distribution hazard ratio 1.57, 95%CI 1.35-1.83). Patients treated with radiotherapy also had an increased risk of cardiovascular mortality (aHR 1.74, 95%CI 1.27-2.37). Hypothetical residual confounders would have to be both strongly associated with non-prostate cancer mortality (HRs > 2.5) and have highly differential prevalence in order to nullify the observed effect.
Among patients carefully matched on cardiovascular risk factors, those treated with radiotherapy had an increased risk of non-prostate cancer mortality and cardiovascular disease. Due to the observational nature of the data, the potential for confounding remains. The magnitude and prevalence of potential residual confounders required to account for differences in treatment effects for prostate cancer was quantified.
Urology. 2018 Jan 02 [Epub ahead of print]
Christopher J D Wallis, Raj Satkunasivam, Sender Herschorn, Calvin Law, Arun Seth, Ronald T Kodama, Girish S Kulkarni, Robert K Nam
Division of Urology, Sunnybrook Health Sciences Centre, Sunnybrook Research Institute, University of Toronto, 2075 Bayview Ave, Toronto, Ontario, Canada, M4N 3M5; Institute of Health Policy, Management, & Evaluation, University of Toronto, 155 College St, Suite 425, Toronto, Ontario, Canada, M5T 3M6. Electronic address: ., Division of Urology, Sunnybrook Health Sciences Centre, Sunnybrook Research Institute, University of Toronto, 2075 Bayview Ave, Toronto, Ontario, Canada, M4N 3M5., Institute of Health Policy, Management, & Evaluation, University of Toronto, 155 College St, Suite 425, Toronto, Ontario, Canada, M5T 3M6; Division of General Surgery, Sunnybrook Health Sciences Centre, Sunnybrook Research Institute, University of Toronto, 2075 Bayview Ave, Toronto, Ontario, Canada, M4N 3M5., Department of Anatomic Pathology, Platform Biological Sciences, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Ave, Toronto, Ontario, Canada, M4N 3M5., Institute of Health Policy, Management, & Evaluation, University of Toronto, 155 College St, Suite 425, Toronto, Ontario, Canada, M5T 3M6; Division of Urology, University Health Network, University of Toronto, 149 College St, Room 503G, Toronto, Ontario, Canada, M5T 1P5., Division of Urology, Sunnybrook Health Sciences Centre, Sunnybrook Research Institute, University of Toronto, 2075 Bayview Ave, Toronto, Ontario, Canada, M4N 3M5; Institute of Health Policy, Management, & Evaluation, University of Toronto, 155 College St, Suite 425, Toronto, Ontario, Canada, M5T 3M6. Electronic address: .
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