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

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.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 and5 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 and3 mm) and all seven categories was correlated with iPSA and Bx parameters. Logistic and linear regression were used to analyze the data.Patients' median age and iPSA were 59 years and 5.28 ng ml(-1), respectively. PCa-to-urethra distance was5 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 (P0.0001), BxGS (P=0.0016), number of positive cores (P0.0001), highest percentage of PCa/cores (P0.0001), bilateral disease (P=0.0003), PNI (P=0.01) and PCa detected in biopsies from apex (P0.0001), 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 (P0.0001) with both versions of PCa-to-urethra distance.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.