A quantitative imaging biomarker is desirable to provide a comprehensive measure of whole-body tumor burden in patients with metastatic prostate cancer, and to standardize the evaluation of treatment-related changes. Therefore, we evaluated whether prostate-specific membrane antigen (PSMA) ligand PET/CT may be applied to provide PSMA-derived volumetric parameters for quantification of whole-body tumor burden. One hundred one patients who underwentGa-PSMA I&T PET/CT because of increasing prostate-specific antigen (PSA) levels after radical prostatectomy were included in this retrospective analysis. Tracer uptake was quantified using SUVs. Volumetric parameters, that is, PSMA-derived tumor volume (PSMA-TV) and total lesion PSMA (TL-PSMA), were calculated for each patient using a 3-dimensional segmentation and computerized volumetry technique and compared with serum PSA levels. In a group of 10 patients, volumetric parameters were applied for treatment monitoring. Volumetric parameters, that is, whole-body PSMA-TV and whole-body TL-PSMA, demonstrated a statistically significant correlation with PSA levels ( < 0.0001) as a surrogate marker of tumor burden, whereas SUV ( = 0.22) or SUV ( = 0.45) did not. Treatment response and treatment failure were paralleled by concordant changes in both whole-body PSMA-TV and whole-body TL-PSMA ( = 0.02), whereas neither the change in SUV ( = 1.0) nor the change in SUV ( = 1.0) concordantly paralleled changes in PSA levels. PSMA-derived volumetric parameters provide a quantitative imaging biomarker for whole-body tumor burden, capable of standardizing quantitative changes in PET imaging of patients with metastatic prostate cancer and of facilitating therapy monitoring.

ERBT is safe and reliable regardless of the energy source and provides high-quality resections of tumors >1 cm. Recurrence rates did not differ between groups, and the majority of recurrences occurred outside the ERBT resection field.

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Preliminary results in the presented cohort suggest that radiotherapy based on (68)Ga-PSMA ligand PET/CT yields effective local control and significant treatment response in terms of PSA levels in the absence of clinically important side effects. Furthermore, this approach delayed the necessity of androgen deprivation therapy or systemic therapy.

Primary prostate cancer is readily identified on early dynamic and static delayed Ga-PSMA ligand PET images. The tumor-to-nontumor ratio in the prostate gland improves over time, supporting a role of delayed imaging for optimal visualization of prostate cancer.