Characteristics of Radiopharmaceutical Uptake in Primary Tumor and Metastatic Lesions of Prostate Carcinoma: Comparison of Oligometastatic with Multimetastatic Disease.

OBJECTIVES: Oligometastases may generate secondary to indolent tumor biology. In this study, we investigated whether semiquantitative measures of 18 F-fluorodeoxyglucose (FDG) and gallium-68 (68 Ga) prostate-specific membrane antigen (PSMA) uptake of metastatic lesions and prostatic sites are different between oligometastatic (OM) and multimetastatic (MM) disease of prostate carcinoma (PC).

METHODS: Patients with PC, who underwent positron emission tomography/computed tomography (PET/CT) from October 2012 to February 2020 were retrospectively reviewed. Patients, whose reports were consistent with metastatic diseases were selected. Patients classified as with MM or OM disease. Maximum standardized uptake values (SUVmax ) were calculated from metastatic lesions and the prostatic site. The median of the SUVmax results between patients with OM and MM disease were compared.

RESULTS: A totally 145 patients with a mean age of 71.46±9.26, were evaluated. In 59 of 145 patients, 18 F-FDG PET/CT was performed;86 patients had gone through 68 Ga PSMA PET/CT. Thirty-seven of 145 patients were OM, whereas 108 patients were MM. The median of the SUVmax of metastatic lesions in patients with OM and MM disease in the 18 F-FDG group were 5.60 and 9.51, respectively. The results of the calculated median SUVmax values in OM and MM disease in the Ga-68 PSMA group were 13.44 and 29.84, respectively. A significant difference was observed in the median SUVmax results of metastatic lesions between OM and MM disease (p<0.05). Median values of SUVmax calculated from the prostatic site in OM and MM disease were 7.83 and 12.29 respectively in 18 F-FDG; 26.23 and 26.74 in the 68 Ga PSMA group. No significant difference was found in the SUVmax results of the prostatic site between OM and MM disease (p>0.05).

CONCLUSION: SUVmax results of metastatic lesions are significantly higher in patients with MM than in patients with OM disease in patients with PC, which may be secondary to their different biological contents in terms of aggressiveness.