Objective
To assess the association between local treatment modality, surgery or radiotherapy,
and non–prostate cancer and cardiovascular mortality in patients treated for nonmetastatic
prostate cancer, given the high competing risk of mortality in this population.
Methods
We performed a population-based, retrospective cohort study of men treated for nonmetastatic
prostate cancer in Ontario, Canada, from 2002 to 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 and Gray subdistribution 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.
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 subdistribution hazard ratio [HR] 1.57, 95% confidence interval 1.35-1.83).
Patients treated with radiotherapy also had an increased risk of cardiovascular mortality
(adjusted HR 1.74, 95% confidence interval 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 to nullify the observed effect.
Conclusion
Among patients carefully matched on cardiovascular risk factors, those treated with
radiotherapy had an increased risk of non–prostate cancer mortality and cardiovascular
disease. Because of 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.
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Article info
Publication history
Published online: January 02, 2018
Accepted:
December 8,
2017
Received:
October 27,
2017
Footnotes
Financial Disclosure: The authors declare that they have no relevant financial interests.
Identification
Copyright
© 2017 Elsevier Inc. All rights reserved.
