Detection of metastases in newly diagnosed prostate cancer by using 68Ga-PSMA PET/CT and its relationship with modified D'Amico risk classification.

We aimed to investigate the diagnostic power of 68Ga-PSMA PET/CT in the detection of metastatic spread of newly diagnosed PCa, and evaluate the relationship with modified D'Amico risk classification.

We evaluated newly diagnosed PCa patients who underwent 68Ga-PSMA PET/CT prior to therapy. All images were interpreted retrospectively and areas of abnormally increased tracer uptake were documented according to PSMA-RADS version 1.0 system. Patients were divided into risk groups as low, intermediate, or high risk, according to a modification in D'Amico classification system as ISUP grade 3 tumors were included to high-risk group. 68Ga-PSMA PET/CT findings were compared among risk groups as well as PSA levels, clinical T stages, and ISUP grades.

A total of 356 patients were included to the study with a median PSA level was 16.42 (1.29-7013) ng/ml and median Gleason score was 8 (range: 6-10). Of these, 13(3.7%), 54 (15.1%), and 289 (81.2%) were in the low-, intermediate-, and high-risk groups, respectively. Lymph node metastases were detected in 125 (35.1%) patients, and in 48 of them, metastasis was limited to pelvic lymph nodes (PLN). Sensitivity, specificity, accuracy, positive predictive value, and negative predictive value were calculated as 71.4%, 100%, 95.9%, 100%, and 95.4%, respectively for the detection of PLN, based on histopathological results of 49 patients. Overall, any metastasis was detected in 47.7% of high-risk patients, while only PLN metastases were defined in 3.7% intermediate-risk patients and none of low-risk patients had any kind of metastasis.

This study revealed that 68Ga-PSMA PET/CT should be routinely used in newly diagnosed high-risk PCa patients; whereas it seems to be of limited use for intermediate-risk group and useless for the low-risk group.

European journal of nuclear medicine and molecular imaging. 2020 Aug 13 [Epub ahead of print]

Duygu Has Simsek, Yasemin Sanli, Muge Nur Engin, Selcuk Erdem, Oner Sanli

Istanbul Faculty of Medicine, Department of Nuclear Medicine, Istanbul University, 34093, İstanbul, Fatih, Turkey. ., Istanbul Faculty of Medicine, Department of Nuclear Medicine, Istanbul University, 34093, İstanbul, Fatih, Turkey., Istanbul Faculty of Medicine, Department of Urology, Istanbul University, 34093, İstanbul, Fatih, Turkey.