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

Abstract

Purpose 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. Methods 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. Results 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. Conclusion 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.