Authors of a new study published Sept. 20 in the Journal of Nuclear Medicine argue that gallium-68 (68Ga) prostate-specific membrane antigen (PSMA)-11 PET/CT imaging can offer additional insight into bone metastases in prostate cancer patients and should be more widely used.
Kelsey L. Pomykala, MD, with the University of California Los Angeles, and colleagues found nearly 18% of patients with serum PSA levels of <5.0 ng/mL had PSMA-positive lesions suspicious for bone metastases. They also found a “higher than expected” incidence of PSMA-positive bone lesions in patients with serum levels ranging from 5-10 ng/mL to 10-20 ng/mL.
“The considerable number of patients with PSMA-positive bone lesions at low PSA levels suggest that indications for bone staging require adaptation,” the researchers wrote.
The efficacy of 68Ga-PSMA-11 PET/CT imaging to identify bone metastases is well known, but experts aren’t sure how bone lesion incidence differs among initial staging, biochemical recurrence or restaging of known metastatic disease. Additionally, there is little known about the association between serum PSA levels, the National Comprehensive Cancer Network (NCCN) risk score, and other markers, such as the Gleason score, and bone involvement.
With that in mind, Pomykala et al. analyzed 388 prostate cancer patients who were enrolled in five prospective studies. Each participants underwent a 68Ga-PSMA-11 PET/CT scan for primary staging, biochemical recurrence localization or restaging between September 2017 and May 2018.
Overall, 27% of patients had a PSMA-positive bone lesion and their incidence was positively associated with serum PSA levels. Bone metastases was most frequent in restaging patients, followed by biochemical recurrence and initial staging patients. Metastasis incidence was not associated with NCCN risk score, the researchers noted.
“The current study demonstrates the importance of initiating a prospective direct comparison between conventional imaging (bone scan, CT, or whole-body MRI, which has replaced bone scans in some institutions) and 68Ga-PSMA-11 PET/CT imaging for bone metastasis staging, and suggests necessary adaptions of bone imaging guidelines in prostate cancer.”