Abstract
PurposeThis study aimed to calculate an applicable relative ratio threshold value instead of the absolute threshold value for simultaneous 68Ga prostate-specific membrane antigen/positron emission tomography ([68Ga]Ga-PSMA-11 PET) in patients with prostate cancer (PCa).Materials and methodsOur study evaluated thirty-two patients and 170 focal prostate lesions. Lesions are classified into groups according to Prostate Imaging Reporting and Data System (PI-RADS). Standardized uptake values maximum (SUVmax), corresponding lesion-to-background ratios (LBRs) of SUVmax, and LBR distributions of each group were measured based on regions of interest (ROI). We examined LBR with receiver operating characteristic analysis to determine threshold values for differentiation between multiparametric magnetic resonance imaging (mpMRI)-positive and mpMRI-negative lesions.ResultsWe analyzed a total of 170 focal prostate lesions. Lesions number of PI-RADS 2 to 5 was 70, 16, 46, and 38. LBR of SUVmax of each PI-RADS scores was 1.5 (0.9, 2.4), 2.5 (1.6, 3.4), 3.7 (2.6, 4.8), and 6.7 (3.5, 12.7). Based on an optimal threshold ratio of 2.5 to be exceeded, lesions could be classified into MRI-positive lesion on [68Ga]Ga-PSMA PET with a sensitivity of 85.2%, a specificity of 72.0%, with the corresponding area under the receiver operating characteristic curve (AUC) of 0.83, p < 0.001. This value matches the imaging findings better.ConclusionThe ratio threshold value of SUVmax, LBR, has improved clinical and research applicability compared with the absolute value of SUVmax. A higher threshold value than the background’s uptake can dovetail the imaging findings on MRI better. It reduces the bias from using absolute background uptake value as the threshold value.
Highlights
Prostate cancer (PCa) is a common malignant disease in the elderly male population
Based on an optimal threshold ratio of 2.5 to be exceeded, lesions could be classified into Magnetic resonance imaging (MRI)-positive lesion on [68Ga]Ga-Prostate-specific membrane antigen (PSMA) Positron emission tomography (PET) with a sensitivity of 85.2%, a specificity of 72.0%, with the corresponding area under the receiver operating characteristic curve (AUC) of 0.83, p < 0.001
The ratio threshold value of Standardized uptake values maximum (SUVmax), lesion-to-background ratios (LBRs), has improved clinical and research applicability compared with the absolute value of SUVmax
Summary
Prostate cancer (PCa) is a common malignant disease in the elderly male population. Approximately 17% of patients with early prostate cancer have metastaticZhao et al Insights Imaging (2020) 11:137 disease. Prostate cancer (PCa) is a common malignant disease in the elderly male population. 17% of patients with early prostate cancer have metastatic. Zhao et al Insights Imaging (2020) 11:137 disease. PCa is the second leading cause of cancer death in men in the western world [1]. Multiparametric magnetic resonance imaging (mpMRI) has been a clinical imaging tool for detecting primary PCa and guiding subsequent biopsy. MpMRI includes T2-weighted imaging (T2WI), diffusionweighted imaging (DWI), apparent diffusion coefficient (ADC), and dynamic contrast-enhanced MRI (DCEMRI). Prostate Imaging Reporting and Data System (PI-RADS) interprets results [2, 3]
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