PSMA- and GRPR-Targeted PET: Results from 50 Patients with Biochemically Recurrent Prostate Cancer

Abstract

Novel radiopharmaceuticals for PET are being evaluated for the diagnosis of biochemical recurrence (BCR) of prostate cancer (PC). We compared the gastrin-releasing peptide receptor-targeting 68Ga-RM2 with the prostate-specific membrane antigen (PSMA)-targeting 68Ga-PSMA11 and 18F-DCFPyL. Methods: Fifty patients underwent both 68Ga-RM2 PET/MRI and 68Ga-PSMA11 (n = 23) or 18F-DCFPyL (n = 27) PET/CT at an interval ranging from 1 to 60 d (mean ± SD, 15.8 ± 17.7 d). SUVmax was collected for all lesions. Results:68Ga-RM2 PET was positive in 35 and negative in 15 of the 50 patients. 68Ga-PSMA11/18F-DCFPyL PET was positive in 37 and negative in 13 of the 50 patients. Both scans detected 70 lesions in 32 patients. Forty-three lesions in 18 patients were identified on only 1 scan: 68Ga-RM2 detected 7 more lesions in 4 patients, whereas 68Ga-PSMA11/18F-DCFPyL detected 36 more lesions in 13 patients. Conclusion:68Ga-RM2 remains a valuable radiopharmaceutical even when compared with the more widely used 68Ga-PSMA11/18F-DCFPyL in the evaluation of BCR of PC. Larger studies are needed to verify that identifying patients for whom these 2 classes of radiopharmaceuticals are complementary may ultimately allow for personalized medicine.

Trial registration: ClinicalTrials.gov NCT02624518 NCT02673151 NCT03501940.

Keywords: 18F-DCFPyL; 68Ga-PSMA11; 68Ga-RM2; PET; prostate cancer.

© 2021 by the Society of Nuclear Medicine and Molecular Imaging.

Figures

Graphical abstract

FIGURE 1.

A 63-y-old man previously treated with radical prostatectomy, followed by salvage RT + ADT, presenting with BCR of PC (PSA, 0.4 ng/mL; PSA velocity, 1.6 ng/mL/y). Maximum-intensity-projection 68Ga-RM2 (A) and 18F-DCFPyL (B) PET images, axial 68Ga-RM2 (C) and 18F-DCFPyL (E) PET images, axial 68Ga-RM2 PET/MR image (D), and axial 18F-DCFPyL PET/CT image (F) are shown. Arrows mark left perirectal lymph nodes with significantly lower 68Ga-RM2 uptake than 18F-DCFPyL uptake.

FIGURE 2.

A 66-y-old man previously treated with RT + ADT, presenting with BCR of PC (PSA, 11.6 ng/mL; PSA velocity, 12.2 ng/mL/y). Maximum-intensity-projection 68Ga-RM2 (A) and 18F-DCFPyL (B) PET images, axial 68Ga-RM2 (C) and 18F-DCFPyL (E) PET images, axial 68Ga-RM2 PET/MR image (D), and axial 18F-DCFPyL PET/CT image (F) are shown. Red arrows mark right adrenal lesion clearly seen on 68Ga-RM2 but not prospectively identified on 18F-DCFPyL, given similar uptake in adrenal gland and liver parenchyma. Blue arrows mark physiologic 68Ga-RM2 uptake in pancreas.