Performance of Ga-68 PSMA PET/CT for diagnosis and grading of local prostate cancer

Abstract

We aimed to evaluate the utility of prostate-specific membrane antigen (PSMA) PET/CT for the detection of local disease within the prostate. This is a retrospective review of a single-center experience evaluating intraprostatic detection rates compared with final histopathology in a radical prostatectomy (RP) population. Seventy-two patients had PSMA PET/CT scan performed as part of their primary staging. Intraprostatic PSMA PET/CT avidity was assessed. PSMA PET/CT uptake was retrospectively correlated with patient characteristics including final histopathology, MRI Prostate Imaging Reporting and Data System (PI-RADS) score, clinical tumor stage, prostate-specific antigen (PSA) level, and patient age. The sensitivity of PSMA PET/CT for the detection of RP-confirmed prostate cancer was 81.2%. Much higher sensitivity was found within certain subpopulations. The patient characteristics that most strongly correlated with focal intraprostatic PSMA PET/CT uptake were patient age (Kendall's tau coefficient τb = 0.24, p < 0.05) and clinical T stage (τb = 0.21, p < 0.05). The International Society of Urological Pathology (ISUP) grade group from final RP was predicted by standardized uptake value (SUVmax) and to a lesser extent PSA and the maximal dimension of PET-avid lesions. SUVmax monotonically increased with ISUP grade group. If SUVmax was above 10 g/mL, the final RP histopathology had a relative risk of 2.3 (95% CI 1.3–4.1) of being ISUP grade group 5. This trial provides early evidence that PSMA PET/CT assists in the grading of prostate cancer and suggests that the imaging modality is particularly accurate in subpopulations including the elderly and those with palpable disease.