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. 2021 Nov 9;11(11):2068.
doi: 10.3390/diagnostics11112068.

Preliminary Results of an Ongoing Prospective Clinical Trial on the Use of 68Ga-PSMA and 68Ga-DOTA-RM2 PET/MRI in Staging of High-Risk Prostate Cancer Patients

Paola Mapelli  1   2 , Samuele Ghezzo  1 , Ana Maria Samanes Gajate  2 , Erik Preza  2 , Giorgio Brembilla  1   3 , Vito Cucchiara  1   4 , Naghia Ahmed  5 , Carolina Bezzi  1   2 , Luca Presotto  2 , Valentino Bettinardi  2 , Annarita Savi  2 , Patrizia Magnani  2 , Raffaele Menichini  2 , Angela Coliva  2 , Ilaria Neri  2 , Ettore Di Gaeta  3 , Luigi Gianolli  2 , Massimo Freschi  5 , Alberto Briganti  1   4 , Francesco De Cobelli  1   3 , Paola Scifo  2 , Maria Picchio  1   2
Affiliations

Preliminary Results of an Ongoing Prospective Clinical Trial on the Use of 68Ga-PSMA and 68Ga-DOTA-RM2 PET/MRI in Staging of High-Risk Prostate Cancer Patients

Paola Mapelli et al. Diagnostics (Basel). .

Abstract

The aim of the present study is to investigate the synergic role of 68Ga-PSMA PET/MRI and 68Ga-DOTA-RM2 PET/MRI in prostate cancer (PCa) staging. We present pilot data on twenty-two patients with biopsy-proven PCa that underwent 68Ga-PSMA PET/MRI for staging purposes, with 19/22 also undergoing 68Gaa-DOTA-RM2 PET/MRI. TNM classification based on image findings was performed and quantitative imaging parameters were collected for each scan. Furthermore, twelve patients underwent radical prostatectomy with the availability of histological data that were used as the gold standard to validate intraprostatic findings. A DICE score between regions of interest manually segmented on the primary tumour on 68Ga-PSMA PET, 68Ga-DOTA-RM2 PET and on T2 MRI was computed. All imaging modalities detected the primary PCa in 18/19 patients, with 68Ga-DOTA-RM2 PET not detecting any lesion in 1/19 patients. In the remaining patients, 68Ga-PSMA and MRI were concordant. Seven patients presented seminal vesicles involvement on MRI, with two of these being also detected by 68Ga-PSMA, and 68Ga-DOTA-RM2 PET being negative. Regarding extraprostatic disease, 68Ga-PSMA PET, 68Ga-DOTA-RM2 PET and MRI resulted positive in seven, four and five patients at lymph-nodal level, respectively, and at a bone level in three, zero and one patients, respectively. These preliminary results suggest the potential complementary role of 68Ga-PSMA PET, 68Ga-DOTA-RM2 PET and MRI in PCa characterization during the staging phase.

Keywords: PET/MRI; PSMA; RM2; hybrid imaging; multimodal imaging; prostate cancer.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Physiological biodistribution of 68Ga-PSMA (A) and 68Ga-DOTA-RM2 (B) in patient n. 3.
Figure 2
Figure 2
A 53 years-old patient with biopsy-proven PCa (pt n. 10), Gleason score 9 (5 + 4) with a PSA level at diagnosis of 3.13 ng/mL. Concordant 68Ga-PSMA PET/MRI (top panel; (A): transaxial 68Ga-PSMA PET; (B): 68Ga-PSMA PET/MRI; (C): Axial T2-weighted sequence; (D): Axial T2-weighted small FOV; (E): DWI (b = 1400)) and 68Ga-DOTA-RM2 PET/MRI (bottom panel; (F): transaxial 68Ga-DOTA-RM2 PET; (G): 68Ga-DOTA-RM2 PET/MRI; (H): axial T2-weighted sequence).
Figure 3
Figure 3
A 75 years-old patient with biopsy-proven PCa (patient n. 3), Gleason score 9 (4 + 5) with a PSA level at diagnosis of 4.73 ng/mL. 68Ga-PSMA and 68Ga-DOTA-RM2 PET/MRI were discordant in detecting lymphnodal metastases. 68Ga-PSMA PET/MRI (top panel; (A): transaxial 68Ga-PSMA PET; (B): 68Ga-PSMA PET/MRI; (C): post-contrast Water Lava-Flex sequence) showed bilateral pararectal and left external iliac lymphnodal uptake; 68Ga-DOTA-RM2 PET/MRI (bottom panel; (D): transaxial 68Ga-DOTA-RM2 PET; (E): 68Ga-DOTA-RM2 PET/MRI; (F): Water-Lava Flex sequence) showed left pararectal and left external iliac lymphnodal uptake. White arrow indicates the lymph node clearly detected by both tracers; red arrows lymph nodes detected by 68Ga-PSMA PET/MRI only.
Figure 4
Figure 4
Venn diagram showing the true-positive, false-positive, true-negative and false-negative findings regarding lymph node involvement for all the investigated imaging modalities using histopathological specimens acquired during radical prostatectomy as ground truth.
Figure 5
Figure 5
A 59 years-old patient with biopsy-proven PCa (patient n. 6), Gleason score 9 (4 + 5) with a PSA level at diagnosis of 11.0 ng/mL. 68Ga-PSMA PET/MRI (top panel; (A): 68Ga-PSMA PET/MRI; (B): axial T2-weighted sequence of the pelvis; (C): axial DWI (b = 1000) displayed with inverted greyscale map) showed increased uptake in correspondence of the left sacral ala, where MRI detected a bone metastasis; 68Ga-DOTA-RM2 PET/MRI (bottom panel; (D): 68Ga-DOTA-RM2 PET/MRI; (E): axial T2-weighted sequence of the pelvis) did not show any 68Ga-DOTA-RM2 in correspondence of the bone metastases.
Figure 6
Figure 6
Images representing concordant (A) and discordant (B) contouring on DICE analysis. (A): A 74 years-old patient with biopsy-proven PCa (pt n. 9), Gleason score 9 (5 + 4) with a PSA level at diagnosis of 6.37 ng/mL presenting a prostatic lesion located in the left lobe of the gland. The image shows a concordant identification of the lesion on 68Ga-PSMA PET images (blue), 68Ga-DOTA-RM2 PET images (yellow) and MRI (red). DICE SCORE: 68Ga-PSMA vs. 68Ga-DOTA-RM2 = 0.6019, 68Ga-PSMA vs. MRI = 0.7581. 68Ga-DOTA-RM2 vs. MRI = 0.7220. (B): A 52 years-old patient with biopsy-proven PCa (pt n. 14), Gleason score 8 (4 + 4) with a PSA level at diagnosis of 8.04 ng/mL presenting a focal left prostatic. DICE SCORE: 68Ga-PSMA vs. 68Ga-DOTA-RM2 = 0.2918, 68Ga-PSMA vs. MRI = 0.6162. 68Ga-DOTA-RM2 vs. MRI = 0.2216.
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