68Ga-PSMA and 68Ga-DOTA-RM2 PET/MRI in Recurrent Prostate Cancer: Diagnostic Performance and Association with Clinical and Histopathological Data

Abstract

The aim of the present study is to investigate and compare the performances of 68Ga-PSMA and 68Ga-DOTA-RM2 PET/MRI in identifying recurrent prostate cancer (PCa) after primary treatment and to explore the association of dual-tracer PET findings with clinical and histopathological characteristics. Thirty-five patients with biochemical relapse (BCR) of PCa underwent 68Ga PSMA PET/MRI for restaging purpose, with 31/35 also undergoing 68Ga-DOTA-RM2 PET/MRI scan within 16 days (mean: 3 days, range: 2–16 days). Qualitative and quantitative image analysis has been performed by comparing 68Ga-PSMA and 68Ga-DOTA-RM2 PET/MRI findings both on a patient and lesion basis. Clinical and instrumental follow-up was used to validate PET findings. Fisher’s exact test and Mann-Whitney U test were used to investigate the association between dual-tracer PET findings, clinical and histopathological data. p-value significance was defined below the 0.05 level. Patients’ mean age was 70 years (range: 49–84) and mean PSA at time of PET/MR scans was 1.88 ng/mL (range: 0.21–14.4). A higher detection rate was observed for 68Ga-PSMA PET/MRI, with more lesions being detected compared to 68Ga-DOTA-RM2 PET/MRI (26/35 patients, 95 lesions vs. 15/31 patients, 41 lesions; p = 0.016 and 0.002). 68Ga-PSMA and 68Ga-DOTA-RM2 PET/MRI findings were discordant in 11/31 patients; among these, 10 were 68Ga-PSMA positive (9/10 confirmed as true positive and 1/10 as false positive by follow-up examination). Patients with higher levels of PSA and shorter PSA doubling time (DT) presented more lesions on 68Ga-PSMA PET/MRI (p = 0.006 and 0.044), while no association was found between PET findings and Gleason score. 68Ga-PSMA has a higher detection rate than 68Ga-DOTA-RM2 in detecting PCa recurrence. The number of 68Ga-PSMA PET positive lesions is associated with higher levels of PSA and shorter PSA DT, thus representing potential prognostic factors.

Correlation of68Ga-RM2 PET with Postsurgery Histopathology Findings in Patients with Newly Diagnosed Intermediate- or High-Risk Prostate Cancer

“…Although the detection rate of 95% for the primary tumor is similar that in to our study, the positivity rates for lymph nodes were lower (37% for 68 Ga-PSMA11, 21% for 68 Ga-RM2). Apart from a negative 68 Ga-RM2 finding in 1 participant, concordant uptake was seen between 68 Ga-RM2 and 68 Ga-PSMA11 (38). The incongruent uptake pattern in our cohort might be due to our more heterogeneous groups of intermediate-and high-risk PC.…”

68Ga-PSMA-11 PET/CT versus 68Ga-PSMA-11 PET/MRI for the detection of biochemically recurrent prostate cancer: a systematic review and meta-analysis

“…There were still 55 studies for full-text screening, and another 18 were disqualified due to the following reasons: non-English studies (n = 3); cannot extract positivity rate data (n = 7); and different radiotracers (n = 8). 37 studies that satisfied the criteria for the meta-analysis were finally included, including 25 articles for 68 Ga-PSMA-11 PET/CT (14-38) and 13 articles for 68 Ga-PSMA-11 PET/MRI (4,26,(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49). One of the studies included not only 68 Ga-PSMA-11 PET/CT but also 68 Ga-PSMA-11 PET/MRI.…”

The effects of novel macrocyclic chelates on the targeting properties of the 68Ga-labeled Gastrin releasing peptide receptor antagonist RM2

“…A small peptide called RM2, with the chelator DOTA coupled to D-Phe-Gln-Trp-Ala-Val-Gly-His-Sta-Leu-NH2 via the cationic spacer 4-amino-1-carboxymethyl-piperidine (referred to as DOTA-RM2 in this study), has shown to be one of the potent antagonists with excellent pharmacokinetic properties, indicating that gallium-68 labeled DOTA-RM2 may serve as a good candidate for positron emission tomography (PET) imaging [ 15 ]. Currently, GRPr imaging appears to be complementary to prostate-specific membrane antigen (PSMA) imaging in preclinical studies and preliminary human studies in patients with primary limited prostate cancer [ 16 , 17 ]. Several studies have shown that in recurrent prostate cancer, RM2-PET imaging may be more beneficial in patients with negative findings on conventional imaging, compared to PSMA-PET [ 18 – 20 ].…”