68Ga-RM2 PET in PSMA- positive and -negative prostate cancer patients

Abstract

Aim 68Ga-PSMA-11 is the gold standard for molecular imaging of prostate cancer. However, recurrent tumor manifestations or metastases cannot be detected in every case. Therefore, we investigated if there is an additive value of the gastrin-releasing peptide receptor (GRP-R) ligand 68Ga-RM2 compared to the well-established 68Ga-PSMA-11 in patients with (Group 1) and without (Group 2) pathologic PSMA-expression in different tumor stages. Patients and Methods Sixteen men (median age: 74 years, range 50–80 years) with prostate cancer in different stages who had a recent negative (n = 8) or pathologic (n = 8) PSMA PET underwent a subsequent 68Ga-RM2 PET. Both examinations were analyzed qualitatively and quantitatively and compared in terms of pathologic and physiologic tracer distribution. Results None of the PSMA-negative patients showed any pathological RM2-accumulation. Pathologic PSMA-uptake was observed in 8 patients of whom 5 had pathologic RM2-uptake. The number of patients with a local recurrence was equal in both scans (n = 3). Bone metastases and lymph node metastases were detected in less patients in RM2 PET compared to PSMA PET (n = 4 vs. 7 and n = 2 vs. 5, respectively). In one patient, PSMA-positive liver metastases were not detected in RM2. RM2 PET revealed two additional lesions indicative for bone metastases in two patients with multiple PSMA-positive bone metastases, which had no therapeutic consequence. Conclusion At least in our small and heterogeneous patient population, 68Ga-RM2 showed no clinically relevant, additional benefit compared to 68Ga-PSMA-11 PET.

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

“…Participants with suspected BCR PC after primary treatment were prospectively enrolled in 3 clinical trials evaluating the performance of 68 Ga-RM2 (NCT 02624518), 68 Ga-PSMA11 (NCT02673151) and 18 F-DCFPyL (NCT03501940). Twenty-three patients had both 68 Ga-RM2 PET/MRI and 68 Ga-PSMA11 PET/CT, while another 27 patients had both 68 Ga-RM2 PET/MRI and 18 F-DCFPyL PET/CT.…”

“…Commonly used radiopharmaceuticals targeting PSMA include 68 Ga-PSMA-HBED-CC ( 68 Ga-PSMA11) (6) and 18 F-DCFPyL (7). Another class of radiopharmaceuticals used for the assessment of PC patients are the gastrin releasing peptide (GRP) analogs.…”

More Than Meets the Eye: Scientific Rationale behind Molecular Imaging and Therapeutic Targeting of Prostate-Specific Membrane Antigen (PSMA) in Metastatic Prostate Cancer and Beyond

“…However, high interindividual variability of agreement between the uptake of this radioligand and histopathology has been observed [ 164 ]. In a study comparing 68 Ga-PSMA-11 with 68 Ga-RM2, no PSMA-negative patients showed RM2-accumulation [ 165 ]. Both 68 Ga-PSMA-11 and 68 Ga-RM2 identified the same cases of local recurrence, but 68 Ga-RM2 scans were negative in some of the patients with PSMA-positive bone or lymph node metastases.…”

“…Both 68 Ga-PSMA-11 and 68 Ga-RM2 identified the same cases of local recurrence, but 68 Ga-RM2 scans were negative in some of the patients with PSMA-positive bone or lymph node metastases. 68 Ga-RM2 scans did reveal some additional metastatic bone lesions but did not affect the line of treatment [ 165 ]. Theranostic 177 Lu-RM2 therapy was well tolerated in mCRPC patients with the pancreas being the critical organ [ 166 ].…”

Prostate incidentaloma on 18F-fluorodeoxyglucose positron emission tomography: Diagnostic value of volumetric positron emission tomography parameters

“…There is, therefore, a high detecting potential as a second primary cancer in the clinical follow-up of other malignancies. Malignancy is present in a significant portion of PIs occasionally encountered in routine 18F-FDG PET/CT scans [2,3,12,14,16]. According to a meta-analysis investigating six studies comprising 47,925 patients, the pooled prevalence of incidental prostatic uptake detected using 18F-FDG PET/CT was 1.8 % (95 % CI: 1.3-2.3) and the malignancy ratio of PI was 17 % (95 % CI: 1.3-2.3) [5].…”