Extent of disease in recurrent prostate cancer determined by [68Ga]PSMA-HBED-CC PET/CT in relation to PSA levels, PSA doubling time and Gleason score

Purpose To examine the relationship between the extent of disease determined by [Ga-68]PSMA-HBED-CC-PET/CT and the important clinical measures prostate-specific antigen (PSA), PSA doubling time (PSAdt) and Gleason score. Methods We retrospectively studied the first 155 patients with recurrent prostate cancer (PCA) referred to our university hospital for [Ga-68]PSMA-HBED-CC PET/CT. Results PET/CT was positive in 44 %, 79 % and 89 % of patients with PSA levels of <= 1, 1 - 2 and >= 2 ng/ml, respectively. Patients with high PSA levels showed higher rates of local prostate tumours (p < 0.001), and extrapelvic lymph node (p = 0.037) and bone metastases (p = 0.013). A shorter PSAdt was significantly associated with pelvic lymph node (p = 0.026), extrapelvic lymph node (p = 0.001), bone (p < 0.001) and visceral (p = 0.041) metastases. A high Gleason score was associated with more frequent pelvic lymph node metastases (p = 0.039). In multivariate analysis, both PSA and PSAdt were independent determinants of scan positivity and of extrapelvic lymph node metastases. PSAdt was the only independent marker of bone metastases (p = 0.001). Of 20 patients with a PSAdt <6 months and a PSA >= 2 ng/ml, 19 (95 %) had a positive scan and 12 (60 %) had M1a disease. Of 14 patients with PSA <1 ng/ml and PSAdt >6 months, only 5 (36 %) had a positive scan and 1 (7 %) had M1a disease. Conclusion [Ga-68]PSMA-HBED-CC PET/CT will identify PCA lesions even in patients with very low PSA levels. Higher PSA levels and shorter PSAdt are independently associated with scan positivity and extrapelvic metastases, and can be used for patient selection for [Ga-68]PSMA-HBED-CC PET/CT.