Background: Smaller prostates have been linked to unfavorable clinical characteristics and poor short-term outcomes following radical prostatectomy (RP). We examined the relation between prostate weight at RP and prostate cancer (PC) outcomes post-RP. Methods: Men in the SEARCH cohort undergoing RP between 1988 and 2017 (N = 6242) were studied for PC-specific mortality (PCSM) as the primary outcome, and for biochemical recurrence (BCR), castration-resistant PC (CRPC) and metastasis as secondary outcomes. Hazard ratios (HR) and 95% confidence intervals (CI) were determined for associations between prostate weight and outcomes using Fine-Gray competing risk regression multivariable analyses. Sensitivity analyses were also carried out following exclusion of: (i) men with extreme prostate weights (<20 g and ≥100 g); and (ii) men with elevated prostate specific antigen (PSA) levels. Results: Median values for age, pre-RP PSA and prostate weight were 63 years, 6.6 ng/ml, and 42.0 g, respectively. During a median follow-up of 7.9 years, 153 (3%) died from PC, 2103 (34%) had BCR, 203 (3%) developed CRPC, and 289 (5%) developed metastases. Prostate weight was not associated with PCSM in the main analyses (multivariable HR = 1.43; 95% CI: 0.87–2.34) or in sensitivity analyses. Prostate weight was inversely associated with BCR in the main analyses (multivariable HR = 0.70; 95%CI: 0.61–0.79) which was unchanged in sensitivity analyses. HRs for prostate weight and CRPC and metastasis were elevated but statistical significance was not attained. Similar results were observed in sensitivity analyses. Conclusions: Inconsistent results for prostate weight and short-term vs longer-term outcomes highlight the need to better understand the complex biology leading to prostate size and the relevance of prostate size as a predictor of PC outcomes.
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