Usefulness of Ga-68 HBED-CC PSMA PET/CT for Tumor Staging in theInitial Diagnostic Assessment of Prostate Cancer

Abstract

Purpose: To evaluate the identification of early prostate cancer by Ga-68 HBED-CC PSMA positron emission tomography/computed tomography (PET/CT) using the TNM classification for orientation. Method: Sixteen men with a mean age of 68 ± 6.8 years (range, 55-80 years) who underwent Ga-68 HBED-CCPSMA PET/CT for initial diagnostic evaluation of suspected prostate cancer and biopsy at our department betweenAugust 2013 and June 2015 were included. Cancer extent determined by PET/CT and CT was retrospectively assessed by two independent observers (O2, O3) without knowledge of clinical findings and compared with the initial diagnosis (O1). Histology of the prostate and of suspected metastatic lesions in conjunction with the interdisciplinary TNM diagnosis served as the gold standard. Results: The TNM staging based on morphologic imaging criteria agreed with the gold standard for O1/O2/O3 in 38%/31%/50% of cases for PET/CT and in 19%/13%/13% for CT. Detection rates for O1/O2/O3 were 38/44%/56% versus 19%/19%/13% for T-stage (PET/CT versus CT), 81%/75%/81% versus 75%/63%/75% for N-stage, and 100%/100%/100% versus 100%/88%/100% for M-stage. Compared with histopathology, the TNM stage was underestimated with PET/CT (42%) and even more so with CT alone (81%). Conclusion: Ga-68 HBED-CC PSMA PET/CT appears to be superior to CT alone in determining the TNM stage of prostate cancer, specifically with regard to the T-stage. Nevertheless, even Ga-68 HBED-CC PSMA PET/CT appears to be limited for characterization of the primary tumor and tends to underestimate the T-stage.