Radiother Oncol 2018 May 03
Contouring of prostate tumors on multiparametric MRI: Evaluation of clinical delineations in a multicenter radiotherapy trial.
Abstract
Purpose
To date no guidelines are available for contouring prostate cancer inside the gland, as visible on multiparametric (mp-) MRI. We assessed inter-institutional differences in interpretation of mp-MRI in the multicenter phase III FLAME trial.
Methods
We analyzed clinical delineations on mp-MRI and clinical characteristics from 260 patients across three institutes. We performed a logistic regression analysis to examine each institute's weighting of T2w, ADC and Ktrans intensity maps in the delineation of the cancer. As reviewing of all delineations by an expert panel is not feasible, we made a selection based on discrepancies between a published tumor probability (TP) model and each institute's clinical delineations using Areas Under the ROC Curve (AUC) analysis.
Results
Regression coefficients for the three institutes were -0.07, -0.27 and -0.11 for T2w, -1.96, -0.53 and -0.65 for ADC and 0.15, 0.20 and 0.62 for Ktrans, with significant differences between institutes for ADC and Ktrans. AUC analysis showed median AUC values of 0.92, 0.80 and 0.79. Five patients with lowest AUC values were reviewed by a uroradiologist.
Conclusion
Regression coefficients revealed considerably different interpretations of mp-MRI in tumor contouring between institutes and demonstrated the need for contouring guidelines. Based on AUC values outlying delineations could efficiently be identified for review.
Related Questions
If a patient is noted to have multiple PIRADS-4 and PIRAD-5 lesions of the prostate on MRI, do you offer simultaneous integrated boost via FLAME?
It is a reasonable approach to boost multiple lesions. The FLAME protocol allowed for the treatment of multiple GTVs as long as dose constraints could be maintained. These investigators published a separate paper evaluating the contouring on the trial and reported a maximum of 5 lesions boosted in a...
What references do you use for multi-parametric MRI delineation of the GTV in prostate cancer for prostate nodule?
In FLAME, the boost volume was the GTV on mpMRI as judged by the treating physician without any formal contouring guidelines (Kerkmeijer et al., PMID 33471548). There were differences in MRI protocols and physician judgement resulting in significant differences in tumor volumes between centers (van ...