When to perform bone scan in patients with newly diagnosed prostate cancer: external validation of a novel risk stratification tool.

Purpose: To externally validate the performance characteristics of the Briganti's risk stratification tool for baseline staging bone scan in patients with newly diagnosed prostate cancer (PCa).

Methods: From 2009 onwards, a consecutive series of patients with PCa were enrolled. All patients were staged to evaluate the presence of bone metastasis (BM) with a conventional total-body Tc 99 m MDP scintigraphy performed regardless of baseline PCa characteristics. The area under the curve (AUC) estimates were used to test the accuracy of the Briganti's risk stratification tool that recommended staging baseline bone scan for patients with a biopsy Gleason score >7 or with a prostate-specific antigen (PSA) >10 ng/ml and palpable disease (cT2/T3). The new tool was compared to the European Association of Urology (EAU) guideline.

Results: A total of 313 patients were consecutively enrolled. Median age was 68 (range 49-95 years), and median PSA was 7 ng/ml (range 0.81-2,670). Twenty (6.4 %) patients presented BMs. Patients with BMs were significantly older, with higher PSA and a higher Gleason score (p = 0.001). The novel Briganti's model was significantly (p = 0.001) more accurate (AUC: 0.75; CI: 0.632-0.859) than the EAU guideline (AUC: 0.64; CI: 0.52-0.761) for the prediction of BMs.

Conclusions: Our study validated in a group of patients with PCa the novel risk stratification tool proposed by Briganti, which presented a higher accuracy for baseline staging bone scan when compared with the EAU guideline. In our experience, this approach would further reduce (about 60 %) the use of staging baseline bone scan without compromising the ability to detect BMs in patients with PCa.