• José Luis Thenier-Villa, Francisco Ramón Martínez-Ricarte, Margarita Figueroa-Vezirian, and Fuat Arikan-Abelló.
• Department of Neurosurgery, University Hospital Arnau de Vilanova, Lleida, Spain; Department of Neurosurgery, Vall d'Hebron University Hospital, Barcelona, Spain; Neurotrauma and Neurosurgery Research Unit (UNINN), Vall d'Hebron Research Institute (VHIR), Barcelona, Spain. Electronic address: jlthenier.lleida.ics@gencat.cat.
• World Neurosurg. 2024 Mar 1; 183: e953e962e953-e962.

BackgroundOne of the most frequent phenomena in the follow-up of glioblastoma is pseudoprogression, present in up to half of cases. The clinical usefulness of discriminating this phenomenon through magnetic resonance imaging and nuclear medicine has not yet been standardized; in this study, we used machine learning on multiparametric magnetic resonance imaging to explore discriminators of this phenomenon.MethodsFor the study, 30 patients diagnosed with IDH wild-type glioblastoma operated on at both study centers in 2011-2020 were selected; 15 patients corresponded to early tumor progression and 15 patients to pseudoprogression. Using unsupervised learning, the number of clusters and tumor segmentation was recorded using gap-stat and k-means method, adjusting to voxel adjacency. In a second phase, a class prediction was carried out with a multinomial logistic regression supervised learning method; the outcome variables were the percentage of assignment, class overrepresentation, and degree of voxel adjacency.ResultsUnsupervised learning of the tumor in its diagnosis shows up to 14 well-differentiated tumor areas. In the supervised learning phase, there is a higher percentage of assigned classes (P < 0.01), less overrepresentation of classes (P < 0.01), and greater adjacency (55% vs. 33%) in cases of true tumor progression compared with pseudoprogression.ConclusionsTrue tumor progression preserves the multidimensional characteristics of the basal tumor at the voxel and region of interest level, resulting in a characteristic differential pattern when supervised learning is used.Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.

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