Prostate specific membrane antigen (PSMA) PET/CT for radiation planning and response assessment in intracranial high-grade gliomas.

BACKGROUND

Prostate-specific membrane antigen (PSMA) expression has been demonstrated in the tumor microenvironment of high-grade gliomas (HGG). Here, we assessed the utility of PSMA-positron emission tomography (PET) imaging in patients with HGG for radiation therapy (RT) planning and in differentiating tumor progression from post-treatment changes.

METHODS

Patients with HGG (WHO grade 3-4) were included in our prospective PET imaging registry. Analysis was stratified into two cohorts based on clinical indication for PET-Cohort A: RT planning; and Cohort B: evaluation of suspected recurrence. PSMA avidity was quantified using standardized uptake value (SUV) measurements including absolute maximum SUV(SUVmax), and SUV ratio referencing right parotid (SUVRp), and superior sagittal sinus (SUVRsss).

RESULTS

Twenty-seven patients were included (Cohort A, N = 19; Cohort B, N = 8). In Cohort A, all MRI T1 contrast-enhancing lesions were PET avid; with PSMA-avid volume exceeding MRI T1 contrast-enhancing volume in 4 patients (20%). The respective mean lesion SUVmax, SUVRp, and SUVRsss for patients with PSMA avid disease (n = 17) vs those without (n = 2) were 7.2 vs 1.5 (P = .002); 0.6 vs 0.2 (P = .008); and 6.5 vs 1.8 (P = .008). Post-RT mean SUVmax decreased by 25.8% (6.2 to 4.6, P = .005). In Cohort B, PSMA PET accurately identified pathologically confirmed tumor progression (n = 6, mean SUVmax 7.0) and necrosis (n = 1, SUVmax 1.5) in 88% patients.

CONCLUSIONS

PSMA PET avidity, particularly SUVmax, is higher in glioblastoma multiforme (GBM) patients with residual tumor or tumor progression. These findings suggest a potential role for PSMA PET in tumor delineation, aiding in comprehensive coverage of tumor volumes for radiation planning and response assessment to differentiate tumor progression and post-treatment changes.