TY - JOUR T1 - Initial Experience with Volumetric <sup>68</sup>Ga-PSMA I&amp;T PET/CT for Assessment of Whole-Body Tumor Burden as a Quantitative Imaging Biomarker in Patients with Prostate Cancer JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1962 LP - 1968 DO - 10.2967/jnumed.117.193581 VL - 58 IS - 12 AU - Sebastian Schmuck AU - Christoph A. von Klot AU - Christoph Henkenberens AU - Jan M. Sohns AU - Hans Christiansen AU - Hans-Jürgen Wester AU - Tobias L. Ross AU - Frank M. Bengel AU - Thorsten Derlin Y1 - 2017/12/01 UR - http://jnm.snmjournals.org/content/58/12/1962.abstract N2 - 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. Methods: One hundred one patients who underwent 68Ga-PSMA I&amp;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. Results: Volumetric parameters, that is, whole-body PSMA-TV and whole-body TL-PSMA, demonstrated a statistically significant correlation with PSA levels (P &lt; 0.0001) as a surrogate marker of tumor burden, whereas SUVmax (P = 0.22) or SUVmean (P = 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 (P = 0.02), whereas neither the change in SUVmax (P = 1.0) nor the change in SUVmean (P = 1.0) concordantly paralleled changes in PSA levels. Conclusion: 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. ER -