A population study of neutering status as a risk factor for canine prostate cancer.
BACKGROUND
Prostate cancer has been reported to occur more commonly in neutered than intact male dogs in several case series. This study was undertaken to evaluate risk of prostate cancer in a large population database. The hypothesis was that castration is a risk factor for prostate cancer in male companion dogs.


METHODS
Data were derived from recorded visits to North American veterinary teaching hospitals. The Veterinary Medical Databases (VMDB) were queried to yield male dogs with urinary bladder transitional cell carcinoma (TCC), prostate adenocarcinoma (ACA), prostate TCC, prostate carcinoma (CA), and prostate tumors. A second query yielded all male dogs over the age of 4 years without a diagnosis of urinary tract cancer. These populations were compared to determine relative risks for developing each disease, singly and collectively, associated with neutering status. Odds ratios were calculated for breed as a risk factor.


RESULTS
Neutered males had a significantly increased risk for each form of cancer. Neutered males had an odds ratio of 3.56 (3.02-4.21) for urinary bladder TCC, 8.00 (5.60-11.42) for prostate TCC, 2.12 (1.80-2.49) for prostate adenocarcinoma, 3.86 (3.13-4.16) for prostate carcinoma, and 2.84 (2.57-3.14) for all prostate cancers. Relative risks were highly similar when cases were limited to those with a histologically confirmed diagnosis.


CONCLUSIONS
Breed predisposition suggests that genetic factors play a role in the development of prostate cancer. The risk associated with being neutered is highest for TCC, supporting previous work identifying the urothelium and ductular rather than acinar epithelium as the source of these tumors.
Bryan
Jeffrey N
JN
Department of Veterinary Medicine and Surgery, University of Missouri, Columbia, Missouri, USA. bryanjn@missouri.edu
Keeler
Matthew R
MR
Henry
Carolyn J
CJ
Bryan
Margaret E
ME
Hahn
Allen W
AW
Caldwell
Charles W
CW
D000230:Adenocarcinoma / Q000453:epidemiology / Q000662:veterinary; D000818:Animals; D002277:Carcinoma / Q000453:epidemiology / Q000662:veterinary; D002295:Carcinoma, Transitional Cell / Q000453:epidemiology / Q000662:veterinary; D004283:Dog Diseases / Q000453:epidemiology* / Q000235:genetics; D004285:Dogs; D020022:Genetic Predisposition to Disease; D008297:Male; D016017:Odds Ratio; D009919:Orchiectomy / Q000009:adverse effects / Q000662:veterinary*; D011471:Prostatic Neoplasms / Q000453:epidemiology / Q000235:genetics / Q000662:veterinary*; D012307:Risk Factors; D013045:Species Specificity; D001749:Urinary Bladder Neoplasms / Q000453:epidemiology / Q000662:veterinary