Are staging bone scans necessary in patients with T3a prostate cancer? A multicentre study

Objective:
Studies reporting increased risk of metastases in T3a disease are based on clinical staging (Digital rectal examination) in the pre-multiparametric–magnetic resonance imaging (MRI) (mp-MRI) era. The aim of our study was to assess the rate of positive bone scans in patients ascribed with T3a prostate cancer on a pre-biopsy mp-MRI.

Methods:
We performed a multicentre, retrospective analysis of all patients with T3a prostate cancer staged by mp-MRI who had a bone scan between January 2017 and April 2020.

Results:
A total of 586 patients were diagnosed with T3a prostate cancer on mp-MRI, with a median age of 71 years (range: 47–87). The median presenting PSA was 11 ng/mL (range: 1–537); 125 patients (21.3%) had a PSA ⩽ 20 and either grade group (GG) 1 or 2 in their prostate biopsy; none of these patients had bone metastases. Eighteen patients (3.1%) were found to have bone metastases: 11 patients had GG ⩾ 3 disease on biopsy and nodal disease, 6 had GG ⩾ 3 without evidence of nodal disease and 1 had a PSA of 103.

Conclusion:
The use of bone scans in patients with T3a prostate cancer staged on mp-MRI but without other evidence of high-risk disease (GG ⩾ 3 and PSA > 20 ng/mL) appears to be unnecessary and could be safely avoided.

Level of evidence:
2b