OBJECTIVE - We aim to investigate the pharmacokinetics and distribution of the recently clinically introduced radioligand (68)Ga-PSMA-11 in men with recurrent prostate cancer (PC) by means of dynamic and whole-body PET/CT.
The correlation between PSA levels and (68)Ga-PSMA-11 PET parameters is also investigated.
METHODS - 31 patients with biochemical failure after primary PC treatment with curative intent (median age 71. 0 years) were enrolled in the analysis. The median PSA value was 2. 0 ng/mL (range = 0. 1 - 130. 0 ng/mL) and the median Gleason score was 7 (range = 5 - 9). 8/31 (25. 8 %) of the included patients had a PSA value < 0. 5 ng/ml. All patients underwent dynamic PET/CT (dPET/CT) scanning (60 min) of the pelvis and lower abdomen as well as whole-body PET/CT with (68)Ga-PSMA-11. dPET/CT assessment was based on qualitative evaluation, SUV calculation, and quantitative analysis based on a two-tissue compartment model and a non-compartmental approach leading to the extraction of fractal dimension (FD).
RESULTS - 22/31 patients (71. 0 %) were (68)Ga-PSMA-11-positive, while 9/31 (29. 0 %) patients were (68)Ga-PSMA-11-negative. The median PSA value in the (68)Ga-PSMA-11-positive group was significantly higher (median = 2. 35 ng/mL; range = 0. 19 - 130. 0 ng/mL) than in the (68)Ga-PSMA-11-negative group (median value: 0. 34 ng/mL; range = 0. 10 - 4. 20 ng/mL). A total of 76 lesions were semi-quantitatively evaluated. PC recurrence-associated lesions demonstrated a mean SUVaverage = 12. 4 (median = 9. 0; range = 2. 2 - 84. 5) and mean SUVmax = 18. 8 (median = 14. 1; range = 3. 1 - 120. 3). Dynamic PET/CT studies of the pelvis revealed the following mean values for the PC recurrence-suspicious lesions: K1 = 0. 26, k3 = 0. 30, influx = 0. 14 and FD = 1. 24. Time-activity curves derived from PC-recurrence indicative lesions revealed an increasing (68)Ga-PSMA-11 accumulation during dynamic PET acquisition. Correlation analysis revealed a moderate, but significant, correlation between PSA levels and the number of lesions detected on (68)Ga-PSMA-11 PET/CT (r = 0. 54) and between PSA levels and SUVaverage (r = 0. 48) or SUVmax (r = 0. 44).
CONCLUSIONS - Ga-PSMA-11 PET/CT demonstrated an overall detection rate of 71. 0 % 60 min p. i. of the radiotracer in a mixed patient population with respect to PSA levels and including patients with very low PSA values. Higher PSA values were associated with a higher detection rate. The tracer uptake in PC-recurrence-indicative lesions is increasing during the 60 minutes of dynamic PET acquisition.
European journal of nuclear medicine and molecular imaging. 2016 Jan 12 [Epub ahead of print]
C Sachpekidis, M Eder, K Kopka, W Mier, B A Hadaschik, U Haberkorn, A Dimitrakopoulou-Strauss
Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center (DKFZ), Heidelberg, Germany. Division of Radiopharmaceutical Chemistry, German Cancer Research Center (DKFZ), Heidelberg, Germany. , Division of Radiopharmaceutical Chemistry, German Cancer Research Center (DKFZ), Heidelberg, Germany. , Division of Nuclear Medicine, University of Heidelberg, Heidelberg, Germany. , Department of Urology, University Hospital Heidelberg, Heidelberg, Germany. , Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center (DKFZ), Heidelberg, Germany. , Clinical Cooperation Unit Nuclear Medicine, German Cancer Research Center (DKFZ), Heidelberg, Germany.