A proposal of a new nomogram for predicting upstaging in contemporary D’Amico low-risk prostate cancer patients

Purpose: Unfavorable prostate cancer (PCa) disease at final pathology affects at least 10 % of D’Amico low-risk patients. Thus, conservative therapies including active surveillance may be wrongfully applied. The purposes were to assess the rate of upstaging in a contemporary cohort of D’Amico low-risk PCa patients and to develop and externally validate a nomogram as upstaging prediction tool in two European cohorts. Methods: Analyses were restricted to 2007 patients who harbored low-risk PCa at ≥10-cores initial biopsy according to D’Amico classification (PSA <10.0 ng/ml, Gleason score <7 and clinical stage ≤T2a). Patients underwent radical prostatectomy at a high-volume center in Hamburg, Germany, from 2010 to 2015. The Hamburg cohort was randomly divided into development (n = 1338) and validation cohorts (n = 669). The development cohort was used to devise a nomogram predicting upstaging, defined as presence of ≥pT3 and/or lymph node invasion. The nomogram was externally validated in two European validation cohorts (Hamburg, n = 669; Milan, n = 465). Results: Upstaging was observed in 187/1338 (14.0 %) of low-risk patients. In multivariable models, four of ten tested variables achieved independent predictor status: age (OR 1.07, 95 % CI 1.04–1.09), PSA (OR 1.21, 95 % CI 1.12–1.31), prostate volume (OR 0.97, 95 % CI 0.96–0.98) and percentage of positive cores (OR 1.02, 95 % CI 1.01–1.03). In external validation, the nomogram demonstrated 70.8 % (Hamburg) and 70.0 % (Milan) accuracy, respectively, with excellent concordance between predicted and observed values. Conclusions: Our proposed nomogram is capable to accurately identify D’Amico low-risk patients at risk of upstaging, utilizing four routinely available clinical variables, age, PSA, prostate volume and percentage of positive biopsy cores. Patient summary: Unfavorable prostate cancer disease at final pathology affects at least 10 % of D’Amico low-risk patients. Thus, we developed and externally validated a new nomogram based on contemporary low-risk prostate cancer patients to accurately identify D’Amico low-risk patients at risk of upstaging. It utilizes four routine variables, age, PSA, prostate volume and percentage of positive biopsy cores