Establishing the pathways and indications for performing isotope bone scans in newly diagnosed intermediate-risk localised prostate cancer - results from a large contemporaneous cohort.

OBJECTIVE: To establish the pattern of isotope bone scan (BS) positivity in a large contemporaneous cohort of patients with newly diagnosed localised prostate cancer and compare with the European Association of Urology (EAU) guidelines, as imaging guidelines and clinical practice for using BS to stage newly diagnosed patients with intermediate-risk localised prostate cancer are not uniform in the literature.

PATIENTS AND METHODS: All patients with newly diagnosed prostate cancer were discussed in a specialist multidisciplinary team meeting and were prospectively entered in a database. Patients were categorised based on D'Amico classification. All intermediate- and high-risk patients had pelvic magnetic resonance imaging and BS unless contraindicated. The BS positivity in each group was analysed and the negative predictive value (NPV) calculated. A cohort of 2720 patients between 2002 and 2015 was retrospectively analysed.

RESULTS: Of 976 patients in the D'Amico intermediate-risk category, 99 had primary Gleason pattern 4. Only one of the 99 patients had a positive BS and there were no positive BS in patients with Gleason primary pattern 3 in the intermediate-risk category. On subgroup analysis, based on prostate-specific antigen (PSA) level and Gleason grade alone, the BS-positivity rate in patients with a PSA level of <20 ng/mL and Gleason primary pattern 4 vs 3 was 6% and 0%, respectively, resulting in 100% NPV for a positive BS with Gleason primary pattern 3 and a PSA level of <20 ng/mL. The importance of clinical T stage (cT) was also noted, as eight of 146 patients had positive BS, who were high risk on cT stage, with a PSA level of <20 ng/mL and Gleason score <8. All eight patients had Gleason primary pattern 4. By limiting BS to the population at risk (all high-risk + intermediate-risk with primary pattern 4), 68 BS per year could have been avoided in a single centre. A limitation was that there was no histological confirmation of bony metastases. Extending the BS recommendation considering the new Gleason Grade Grouping is discussed.

CONCLUSION: This study confirms that a staging BS can be safely avoided in patients with intermediate-risk prostate cancer with Gleason primary pattern 3 and to limit performing BS in all high-risk prostate cancer and in the intermediate-risk group when the primary Gleason pattern is 4, thereby reinforcing the current recommendations of the EAU guidelines.