Abstract
PurposeTo elucidate the usefulness of intravoxel incoherent motion (IVIM)/apparent diffusion coefficient (ADC) parameters in preoperative risk stratification using International Society of Urological Pathology (ISUP) grades.Materials and MethodsForty-five prostate cancer (PCa) patients undergoing radical prostatectomy (RP) after prostate multiparametric magnetic resonance imaging (mpMRI) were included. The ISUP grades were categorized into low-risk (I-II) and high-risk (III-V) groups, and the concordance between the preoperative and postoperative grades was analyzed. The largest region of interest (ROI) of the dominant tumor on each IVIM/ADC image was delineated to obtain its histogram values (i.e., minimum, mean, and kurtosis) of diffusivity (D), pseudodiffusivity (D*), perfusion fraction (PF), and ADC. Multivariable logistic regression analysis of the IVIM/ADC parameters without and with preoperative ISUP grades were performed to identify predictors for the postoperative high-risk group.ResultsThirty-two (71.1%) of 45 patients had concordant preoperative and postoperative ISUP grades. Dmean, D*kurtosis, PFkurtosis, ADCmin, and ADCmean were significantly associated with the postoperative ISUP risk group (all p < 0.05). Dmean and D*kurtosis (model I, both p < 0.05) could predict the postoperative ISUP high-risk group with an area under the curve (AUC) of 0.842 and a 95% confidence interval (CI) of 0.726–0.958. The addition of D*kurtosis to the preoperative ISUP grade (model II) may enhance prediction performance, with an AUC of 0.907 (95% CI 0.822–0.992).ConclusionsThe postoperative ISUP risk group could be predicted by Dmean and D*kurtosis from mpMRI, especially D*kurtosis. Obtaining the biexponential IVIM parameters is important for better risk stratification for PCa.
Highlights
The Gleason scores (GSs) obtained from prostate biopsies or transurethral resection of the prostate (TURP) before radical prostatectomy (RP) are used as treatment guidance for prostate cancers (PCas) by stratifying them into low-risk (GS 6), intermediate-risk (GS 7) and high-risk (GS 8-10) groups
The exclusion criteria were [1] no PCa found in RP specimens (n = 1), [2] concurrent malignancy other than PCa in RP specimens (n = 1), [3] a time interval of more than 90 days between multiparametric magnetic resonance imaging (mpMRI) and RP (n = 5) [16, 18], [4] poor diagnostic quality due to artifact of hip prostheses on mpMRI (n = 0), and [5] no detectable PCa on mpMRI (n = 0)
The higher concordance achieved in this study could be explained by the use of more biopsy cores [12, 13] than in previous studies (10 or fewer), 29% of patients who upgraded or downgraded postoperatively remained misclassified in the risk stratification and could have been potentially misled in the treatment selection if it had been based on the preoperative International Society of Urological Pathology (ISUP) risk group alone
Summary
The Gleason scores (GSs) obtained from prostate biopsies or transurethral resection of the prostate (TURP) before radical prostatectomy (RP) are used as treatment guidance for prostate cancers (PCas) by stratifying them into low-risk (GS 6), intermediate-risk (GS 7) and high-risk (GS 8-10) groups. The International Society of Urological Pathology (ISUP) adopted a new grading system for PCas using GSs 6, 3 + 4, 4 + 3, 8, and 9-10 as grades I, II, III, IV, and V, respectively, to replace the old risk stratification groups (i.e., GS 6, 7, 8-10) [6]. The intermediaterisk group (GS 7) in the old risk stratification system is divided into GS 3 + 4 (grade II) and 4 + 3 (grade III) in the new ISUP grade system because there is a significant difference in recurrence between patients in the two new grades [6].
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