RPS 206 - Advanced prostate cancer imaging

Author Block: H. Duan, V. Ferri, P. Ghanouni, B. Daniel, G. Davidzon, C. Mari Aparici, G. Sonn, C. Kunder, A. Iagaru; Stanford, CA/US
Purpose or Learning Objective: Targeting of lesions seen on multiparametric MRI (mpMRI) improves prostate cancer (PC) detection at biopsy. However, 20-65% of highly suspicious lesions on MRI prove to be false positives (FP) at biopsy. We evaluated the potential utility of 68Ga-PSMA11 and 68Ga-RM2 PET/MRI for biopsy guidance in patients with suspected PC and prior negative biopsy or equivocal MRI.
Methods or Background: Ten men with suspected PC were prospectively enrolled to undergo 68Ga-PSMA11 and 68Ga-RM2 PET/MRI, including mpMRI. The prostate was divided into 12 segments (apex, mid, and base, lateral and medial, respectively, left and right) using PET/MRI data and MIM software. Maximum standardised uptake values (SUVmax) of suspected PC lesions and background for each segment were collected. Biopsies after PET/MRI included 1 core through each of the 12 segments and targeted sampling of any lesions seen on PET.
Results or Findings: PSA and PSA density were 10.77±6.27 ng/mL and 0.19±0.11 ng/mL2, respectively. mpMRI was negative in 5 patients, 4 showed PIRADS 4 and 1 PIRADS 5. 68Ga-PSMA11 identified 25 lesions of which 52% were verified PC and 68Ga-RM2 PET/MRI showed 26 lesions with PC verification in 50%. PET/MRI guided biopsy led to the additional finding of 3 clinically significant tumours and 2 GS 6 cancers. For 68Ga-PSMA11, mean SUVmax for true positives (TP) was slightly higher than FP, however not statistically significant whereas for 68Ga-RM2, SUVmax of TP PC lesions were significantly higher than FP (11.56 ± 9.11 [5.57 40.69] vs 7.93 ± 3.74 [3.7318.21], P=0.007).
Conclusion: Our preliminary results show that 68Ga-PSMA11 and 68Ga-RM2 PET/MRI are feasible for biopsy guidance in suspected PC, and most importantly identified additional clinically significant cancers not seen on mpMRI.
Limitations: This study is limited by the small number of patients.
Ethics committee approval: The ethics committee approval was obtained.
Funding for this study: This study is partially funded by GE Healthcare.

Author Block: N. Sushentsev, M. McLean, A. Warren, T. Barrett, F. A. Gallagher; Cambridge/UK
Purpose or Learning Objective: To identify biological mechanisms underpinning differential hyperpolarised [1-13C]lactate labelling in prostate cancer (PCa) and the benign prostate (BP) in patients undergoing radical prostatectomy following hyperpolarised [1-13C]pyruvate magnetic resonance imaging (HP-13C-MRI).
Methods or Background: All patients underwent 3T HP-13C-MRI, with a signal-to-noise ratio (SNR) of lactate derived from areas of PCa and contralateral BP as derived from whole-mount histopathology (WMH). Multiparametric MRI of the prostate was subsequently performed in the same sitting, with apparent diffusion coefficient (ADC) and Ktrans values extracted from identical regions-of-interest. Matching WMH sections were used for immunohistochemical analysis of monocarboxylate transporters (MCT) 1 and 4. RNAscope was used to quantify mRNA expression of lactate dehydrogenase (LDH) subunits A and B, alongside pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1).
Results or Findings: The study included 8 patients with 10 low-to-intermediate risk lesions. Lactate SNR, Ktrans, and WMP-derived cell density were significantly higher in PCa compared to BP (10.76 vs 1.66, 0.39 min-1 vs 0.11 min-1, and 3227.0 cells/mm2 vs 1944.0 cells/mm2; P<0.0001, 0.002, and 0.005, respectively), and ADC values were significantly lower in PCa compared to BP (922.4 10-6 mm2/s vs 1351.0 10-6 mm2/s; P=0.002). MCT1 and MCT4 did not differ between the two tissue types (P=0.796 and 0.684, respectively). Total LDH density and LDHA/PDHA1 mRNA expression ratio were, however, significantly higher in BP compared to PCa (8483.0 103 copies/mm2 vs 5389.0 103 copies/mm2 and 1.15 vs 0.68; P=0.004 and 0.03, respectively).
Conclusion: Lactate SNR was significantly higher in areas of low-to-intermediate risk PCa despite significant overexpression of glycolytic enzymes in BP. This may be explained by the increased perfusion/permeability and cellularity of tumour areas, leading to the increased hyperpolarised [1-13C]pyruvate delivery and [1-13C]lactate labelling.
Limitations: Not applicable.
Ethics committee approval: NREC East of England, 16/EE/0205.
Funding for this study: This study was funded by the Prostate Cancer UK, CRUK.

Author Block: X. A. G. Ballesteros, A. E. Mercado Sánchez, H. Solis Lara; Monterrey/MX
Purpose or Learning Objective: Prostate cancer is the third leading cause of death in men who die from malignant neoplasia, so new tools are being sought to objectively predict the probability of malignant infiltration of the lymph nodes for the adequate staging of the disease. Radiomics is the process of converting medical images into data allowing the extraction of quantitative characteristics. The aim of the study was the analysis of radiomic features of lymph nodes, using 68Ga-PSMA PET/CT, as a standard reference.
Methods or Background: The design was a retrospective, cross-sectional, analytical study, which was developed with a total of 41 patients with prostate cancer diagnosis randomly selected from a database of 253 patients. 3DSlicer software was used to obtain radiomic features. Sixteen nodes were segmented per patient (pelvis, retroperitoneum, mediastinal, axillary, and cervical). The nodes segmented were those with the highest SUVmax value in the positive studies and those with the highest short axis in the negative studies.
Results or Findings: Thirty-three variables of shape and textural analysis of radiomic tomographic features were found that allow differentiating between positive and negative lymph nodes for malignancy.
Conclusion: Radiomic analysis of lymph nodes in prostate cancer could detect the nodal metastatic disease even in lymph nodes of normal morphology and size.
Limitations: The limitations of our study were the small sample size and that it had a retrospective design, but it was performed by a blinded observer. Also, the PET/CT images were evaluated and segmented by a single observer, so the reproducibility of the results between different observers was not evaluated.
Ethics committee approval: This study was approved by the ethics in investigation committee with the number RA20-00009.
Funding for this study: This study was funded by the radiology department of "Dr. José Eleuterio González" University Hospital.