Safely omitting bone isotope scans in a cohort of grade group 2 prostate cancer

A retrospective review conducted in our urology unit to assess the efficiency for requesting bone scans for newly diagnosed prostate cancer patients, aiming to minimize radiation exposure and avoiding unnecessary investigations as cost effective measure.

A retrospective observational study included 360 patients with newly diagnosed prostate cancer within urology department at Calderdale and Huddersfield NHS Trust from April 2016 to March 2018. Parameters observed were: the prostatic specific antigen (PSA) on diagnosis, Gleason score, staging magnetic resonance imaging, and bone scans. We analyzed the possible correlation of the Gleason score and PSA to determine the risk of bony metastasis. Regarding PSA: Patients were categorized as with PSA <15, PSA ≥15. Regarding Gleason score: Patients were categorized as patients with grade group 1 or 2 and patients with grade group 3 and above. Data recorded was then analyzed using χ²  analysis to determine if results were deemed significant or not.

A total of 360 patients: 91 patients (25%) had positive bony metastasis. While 269 patients (75%) had a clear bone scan. Among patients with grade group 3 or above or having PSA ≥15, 90 patients out of 324 patients had bony metastasis (38%). Among patients with grade group 1 or 2 and PSA <15, only 1 patient out of 36 had bony metastasis (2.7%). Negative predictive value of grade group 1 or 2 and PSA <15 for bony metastasis was 97.22%.

Using a cutoff level of PSA <15 in grade group 1 and 2 seems to be a safe and efficient tool to exclude newly diagnosed prostate cancer patients from having an isotope bone scan for staging purpose.