Are Bone Scans Still Necessary in the Era of PSMA PET Imaging?

Sanchay Jain; Michael Graham

Introduction: Bone scans using Tc99m-labeled MDP/HDP have traditionally been a cornerstone in the metastatic workup of prostate cancer. However, prostate-specific membrane antigen (PSMA) PET imaging with agents such as Ga68-PSMA or F18-DCFPyL is now routinely employed for staging, restaging, and therapy response assessment. This study evaluates if bone scans provide additional diagnostic value or influence clinical management when performed in combination with PSMA-based PET-CT imaging. Methods: In this single-center retrospective study, we identified all patients who underwent both a Tc99m HDP bone scan and PSMA PET-CT imaging (either F18-DCFPyL or Ga68-PSMA) within 60 days of each other between 2018 and 2024. For patients with multiple imaging sets, only the first pair was included. Imaging findings were compared to identify cases with additional or discordant bone scan findings which were PSMA non-avid. We reviewed patient records to assess whether these additional bone scan findings led to further diagnostic workup or management changes. Results: A total of 111 patients were identified. Only 7 (6.3%) patients demonstrated additional or discordant sites of uptake on bone scans that were PSMA non-avid on PSMA imaging. None of these patients had received external beam radiation or radionuclide therapy with Pluvicto or Xofigo before these sets of scans. 1. Only one patient was identified as falsely negative on PSMA PET-CT which showed multiple metastatic sites on bone scan and progressive skeletal metastases as determined by contrast CT scans on follow up, leading to a change in clinical management. 2 & 3. Two patients were determined to be falsely positive sites of uptake in the skull on bone scan due to benign variants. 4 & 5. Two patients had PSMA negative rib lesions which were followed up for 2 and 6 years and remained stable leading to no change in management. 6. One of the patients who had widespread skeletal metastatic disease on PSMA PET-CT and some additional discordant sites of uptake on bone scan, also did not result in treatment change. 7. Lastly, one patient had two additional pelvic sites of uptake on bone scan with no anatomic correlate on SPECT-CT, which was also followed up for 20 months, and no treatment changes were observed. Conclusions: Our findings suggest that bone scans provide minimal additional benefit when used in conjunction with PSMA PET-CT imaging in prostate cancer to identify additional sites of disease and effect treatment change. As PSMA PET-CT has evolved into a standard of care in staging, restaging, and response evaluation in prostate cancer, the routine use of bone scans is unnecessary. Furthermore, from the point of view of pre-treatment planning for Pluvicto, the percentage of PSMA negative disease as identified by bone scan is very small and of questionable significance.

Are Bone Scans Still Necessary in the Era of PSMA PET Imaging?

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