The prevalence and locations of bone metastases using whole-body MRI in treatment-naive intermediate- and high-risk prostate cancer

Objective The aim of this study was to assess the prevalence and distribution of bone metastases in treatment-naive prostate cancer patients eligible for a metastatic workup using whole-body MRI, and to evaluate the results in light of current guidelines. Methods This single-institution, retrospective study included all patients with treatment-naive prostate cancer referred to whole-body MRI during 2016 and 2017. All were eligible for a metastatic workup according to the guidelines: PSA > 20 ng/ml and/or Gleason grade group >= 3 and/or cT >= 2c and/or bone symptoms. The definition of a metastasis was descriptive and based on the original MRI reports. The anatomical location of metastases was registered. Results We included 161 patients with newly diagnosed prostate cancer of which 36 (22%) were intermediate-risk and 125 (78%) were high-risk. The median age and PSA were 71 years (IQR 64-76) and 13 ng/ml (IQR 8-28), respectively. Bone metastases were found in 12 patients (7%, 95% CI: 4-13), and all were high-risk with Gleason grade group >= 4. The pelvis was affected in 4 patients, and the spine + pelvis in the remaining 8. No patients demonstrated metastases to the spine without concomitant metastases in the pelvis. Limitations are the small number of metastases and retrospective design. Conclusion This study suggests that the overall prevalence of bone metastases using the current guidelines for screening is quite low. No metastases were seen in the case of Gleason grade group <= 3, and further studies should investigate if it necessary to screen non-high-risk patients.