Comparison of [(18)F]DCFPyL and [ (68)Ga]Ga-PSMA-HBED-CC for PSMA-PET Imaging in Patients with Relapsed Prostate Cancer

Abstract

Purpose: Gallium-68 (Ga-68)-labeled tracers for imaging expression of the prostate-specific membrane antigen (PSMA) such as the [(68)Ga]Ga-PSMA-HBED-CC have already demonstrated high potential for the detection of recurrent prostate cancer. However, compared to Ga-68, a labeling with fluorine-18 (F-18) would offer advantages with respect to availability, production amount, and image resolution. [(18)F]DCFPyL is a promising F-18-labeled candidate for PSMA-positron emission tomography (PET) imaging that has been recently introduced. In the current study, we aimed to compare [(68)Ga]Ga-PSMA-HBED-CC and [(18)F]DCFPyL for clinical use in biochemically relapsed prostate cancer.

Procedures: In 14 selected patients with PSA relapse of prostate cancer, [(18)F]DCFPyL PET/X-ray computed tomography (CT) was performed in addition to [(68)Ga]Ga-PSMA-HBED-CC PET/CT. A systematic comparison was carried out between results obtained with both tracers with regard to the number of detected PSMA-positive lesions, the standardized uptake value (SUV)max and the lesion to background ratios.

Results: All suspicious lesions identified by [(68)Ga]Ga-PSMA-HBED-CC were also detected with [(18)F]DCFPyL. In three patients, additional lesions were observed using [(18)F]DCFPyL PET/CT. The mean SUVmax in the concordant [(18)F]DCFPyL PSMA-positive lesions was significantly higher as compared to [(68)Ga]Ga-PSMA-HBED-CC (14.5 vs. 12.2, p = 0.028, n = 15). The mean tumor to background ratios (n = 15) were significantly higher for [(18)F]DCFPyL compared to [(68)Ga]Ga-PSMA-HBED-CC using kidney, spleen, or parotid as reference organs (p = 0.006, p = 0.002, p = 0.008), but no significant differences were found using the liver (p = 0.167) or the mediastinum (p = 0.363) as reference organs.

Conclusion: [(18)F]DCFPyL PET/CT provided a high image quality and visualized small prostate lesions with excellent sensitivity. [(18)F]DCFPyL represents a highly promising alternative to [(68)Ga]Ga-PSMA-HBED-CC for PSMA-PET/CT imaging in relapsed prostate cancer.

Fig. 1

Patient no. 12 with a rising PSA level of 3.87 ng/ml. In the past, the patient had retroperitoneal lymph node metastases, which were irradiated. On a Biograph mCT 128 scanner, comparison between a MIP (maximum intensity projection) with [¹⁸F]DCFPyL and b MIP with [⁶⁸Ga]Ga-PSMA-HBED-CC. [¹⁸F]DCFPyL PET/CT clearly demonstrates several additional supradiaphragmatic PSMA-positive lesions. [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT showed the supradiaphragmal lesion in the sternum.

Fig. 2

Patient no. 12, Biograph mCT 128. [¹⁸F]DCFPyL PET/CT (b) was suspicious of an additional lymph node metastasis in the dorsal mediastinum, visible as a normal-sized lymph node in a low-dose CT scan without tracer accumulation on c [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT. d Low-dose CT in bone window and e [¹⁸F]DCFPyL PET/CT were suspicious of a bone metastasis in vertebra Th3, barely detectable in f [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT. h [¹⁸F]DCFPyL PET/CT was clearly suspicious of bone metastasis in the processus xiphoideus sterni, hard to detect in g low-dose CT or i [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT.

Fig. 3

Patient no. 2 with a rising PSA level of 4.7 ng/ml. a Low-dose CT in bone window and b [¹⁸F]DCFPyL PET/CT were suspicious of bone metastasis in vertebra L2, hard to discern in the c [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT. Imaging was performed on a Biograph 16 PET/CT.

Fig. 4

Patient no. 7 with a rising PSA level to 1.3 ng/ml. In the past, the patient had left iliac lymph node dissection with histologically confirmed lymph node metastases. Both tracers have shown a left iliac PSMA-avid lymph node, which was confirmed as metastasis (a–c). Additionally, e the [¹⁸F]DCFPyL PET/CT was suspicious of a second PSMA-positive lymph node below the bifurcation of the v. cava inferior, visible as a normal-sized lymph node on d CT, hard to detected on f [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT. a Low-dose CT scan, b [¹⁸F]DCFPyL PET/CT, and c [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT at the level of the iliacae communes._d Low-dose CT scan, e [¹⁸F]DCFPyL PET/CT, and f [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT at the level of the bifurcation. Imaging was performed on a Biograph 16 PET/CT.

Fig. 5

a Ratio of SUV_max in lesions to SUV_mean in the kidney and b ratio of SUV_max in lesions to SUV_mean in the liver. The blue columns represent [⁶⁸Ga]Ga-PSMA-HBED-CC PET/CT, and the red columns represent [¹⁸F]DCFPyL PET/CT. [¹⁸F]DCFPyL showed a higher tumor to background ratio than [⁶⁸Ga]Ga-PSMA-HBED-CC when the kidney was used as a reference organ (p = 0.006, n = 15). The tumor to background ratio did not differ significantly between [¹⁸F]DCFPyL and [⁶⁸Ga]Ga-PSMA-HBED-CC when the liver was used as a reference organ (p = 0.167, n = 15). LN lymph node metastasis, LR local relapse, BM bone metastasis.