Vasectomy and risk of prostate cancer: population based matched cohort study.
OBJECTIVE
To determine the association between vasectomy and prostate cancer, adjusting for measures of health seeking behaviour.


METHODS
Population based matched cohort study.


METHODS
Multiple validated healthcare databases in Ontario, Canada, 1994-2012.


METHODS
326 607 men aged 20 to 65 who had undergone vasectomy were identified through physician billing codes and matched 1:1 on age (within two years), year of cohort entry, comorbidity score, and geographical region to men who did not undergo a vasectomy.


METHODS
The primary outcome was incident prostate cancer. Secondary outcomes were prostate cancer related grade, stage, and mortality.


RESULTS
3462 incident cases of prostate cancer were identified after a median follow-up of 10.9 years: 1843 (53.2%) in the vasectomy group and 1619 (46.8%) in the non-vasectomy group. In unadjusted analysis, vasectomy was associated with a slightly increased risk of incident prostate cancer (hazard ratio 1.13, 95% confidence interval 1.05 to 1.20). After adjustment for measures of health seeking behaviour, however, no association remained (adjusted hazard ratio 1.02, 95% confidence interval 0.95 to 1.09). Moreover, no association was found between vasectomy and high grade prostate cancer (adjusted odds ratio 1.05, 95% confidence interval 0.67 to 1.66), advanced stage prostate cancer (adjusted odds ratio 1.04, 0.81 to 1.34), or mortality (adjusted hazard ratio 1.06, 0.60 to 1.85).


CONCLUSIONS
The findings do not support an independent association between vasectomy and prostate cancer.
Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, 610 University Ave 3-130, Toronto, ON, M5G 2M9, Canada madhur.nayan@mail.utoronto.ca.
Madhur
M
Nayan
Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, 610 University Ave 3-130, Toronto, ON, M5G 2M9, Canada.
Robert J
RJ
Hamilton
Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.
Erin M
EM
Macdonald
Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.
Qing
Q
Li
Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.|Li Ka Shing Knowledge Institute, St Michael's Hospital, Toronto, ON, Canada.
Muhammad M
MM
Mamdani
Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.|Ontario Institute for Cancer Research, Toronto, ON, Canada.
Craig C
CC
Earle
Division of Urology, Departments of Surgery and Surgical Oncology, Princess Margaret Cancer Centre, University Health Network and the University of Toronto, 610 University Ave 3-130, Toronto, ON, M5G 2M9, Canada.|Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.
Girish S
GS
Kulkarni
Division of Urology, Department of Surgery, Mount Sinai Hospital, University of Toronto, Toronto, ON, Canada; Faculty of Medicine, Institute of Medical Science, University of Toronto, Toronto, ON, Canada; Lunenfeld Tannenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada.
Keith A
KA
Jarvi
Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.|Department of Internal Medicine, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, ON, Canada.
David N
DN
Juurlink
D000328:Adult; D000368:Aged; D015331:Cohort Studies; D006801:Humans; D015994:Incidence; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D011471:Prostatic Neoplasms / Q000453:epidemiology*; D014659:Vasectomy / Q000706:statistics & numerical data*; D055815:Young Adult