Prediction of prostate cancer to urethra distance by a pretreatment nomogram: Urethral thermoprotection implication in cryoablation

Introduction:Cryoablation is a treatment option for prostate cancer (PCa) patients. A urethral warming catheter is placed to protect the prostatic urethra from cryo-injury. Thus tissue within certain depth beneath the urethral mucosa, including PCa in that zone, is not cryoablated. Preoperative predictors of PCa-to-urethra distance are important for urologists and patients to decide if undergoing cryoablation.Methods:A total of 267 consecutive radical prostatectomy specimens were reviewed by a pathologist and the shortest PCa-to-urethra distance was recorded as 0 (PCa at urethra), 0.1-1 mm, 1.1-2 mm, 2.1-3 mm, 3.1-4 mm, 4.1-5 mm and >5 mm. Preoperative serum PSA (iPSA) and prostate biopsy (Bx) parameters such as highest Bx Gleason score (BxGS), number of positive cores, highest percentage of PCa/cores, bilateral disease, perineural invasion (PNI) and PCa location were also recorded. The PCa-to-urethra distance subdivided into two (≤3 and >3 mm) and all seven categories was correlated with iPSA and Bx parameters. Logistic and linear regression were used to analyze the data.Results:Patients' median age and iPSA were 59 years and 5.28 ng ml-1, respectively. PCa-to-urethra distance was <5 mm in 163 (61%) patients, ≤3 mm in 48% of patients. Significant univariate associations were found between shorter PCa-to-urethra distance and increasing iPSA (P<0.0001), BxGS (P=0.0016), number of positive cores (P< 0.0001), highest percentage of PCa/cores (P< 0.0001), bilateral disease (P=0.0003), PNI (P=0.01) and PCa detected in biopsies from apex (P< 0.0001), base (P=0.001) and base/medial base (P= 0.0006). In multivariate analysis, the iPSA (log), highest percentage of PCa/cores and PCa detected in the apex were significantly associated (P<0.0001) with both versions of PCa-to-urethra distance.Conclusions: Increasing iPSA, highest percentage of PCa/cores and PCa detected in the apex were associated with a shorter PCa-to-urethra distance. Inclusion of these preoperative parameters in a nomogram will help estimating the PCa-to-urethra distance and identifying better candidates for cryoablation.