Purpose: To determine the relationship between serum prostate-specific antigen (PSA) level categories (< 5; 5-10; 10-20;>20 ng/ml) and the incidence of bone metastases detected by total-body 68Ga-prostate-specific membrane antigen (PSMA)-11 PET/CT and to assess if expanding the 68Ga-PSMA-11 PET/CT imaging field to include the vertex and lower extremities (total-body acquisition) affects bone metastasis detection rates and patient management. Methods: This is a retrospective analysis of 388 prostate cancer patients enrolled in five prospective studies (NCT02940262, NCT03368547, NCT03042312, UCLA IRB#17-001336, NCT03515577). All underwent 68Ga-PSMA-11 PET/CT scans acquired from vertex to toes for primary staging (n = 93/388, 24%), biochemical recurrence (BCR) localization (n = 225/388, 58%) or re-staging (n = 70/388, 18%) between September 2017 and May 2018. Results: Three hundred and twenty-one of 388 patients (83%) had a positive 68Ga-PSMA-11 study. PSMA-positive bone lesions were found in 105/388 (27%) patients. Their incidence was positively associated with serum PSA levels (< 10 ng/ml: 21%; 10-20 ng/ml: 41%; ≥ 20 ng/ml: 41%, p-value <0.001). This association was maintained for all three indications; initial staging, BCR and re-staging. Bone metastases occurred most frequently in re-staging patients, followed by BCR and initial staging patients. Bone metastasis incidence was not significantly associated with NCCN risk score (P = 0.22). The average number of PSMA-positive regions also increased with serum PSA levels (p<0.001). Eighteen of 388 (5%) and 18/388 (5%) had lesions above the superior orbital ridge and below the proximal third of the femur, respectively. There was only 1/388 patient (0.26%) in whom the total-body PET acquisition had an impact on management. Conclusion: Bone metastases as assessed with 68Ga-PSMA-11 PET/CT are prevalent even in patients with low serum PSA levels. Therefore, current guidelines for bone assessments in prostate cancer patients should be revisited as 68Ga-PSMA-11 PET/CT may provide additional information for accurate bone staging at low serum PSA levels. Including the total-body (from vertex to toes) for 68Ga-PSMA-11 PET/CT imaging revealed additional bone lesions in 6% of patients, however, without significantly affecting patient management.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2019 Sep 20 [Epub ahead of print]

Kelsey Lynn Pomykala, Johannes Czernin, Tristan R Grogan, Wesley R Armstrong, John Willliams, Jeremie Calais

Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, United States., Department of Medicine Statistics Core, David Geffen School of Medicine, UCLA.