Methodological framework for radiomics applications in Hodgkin’s lymphoma

Background:According to published data, radiomics features differ between lesionsof refractory/relapsing HL patients from those of long-term responders. However,several methodological aspects have not been elucidated yet.Purpose:The study aimed at setting up a methodological framework in radiomicsapplications in Hodgkin’s lymphoma (HL), especially at (a) developing a novel featureselection approach, (b) evaluating radiomic intra-patient lesions’similarity, and (c)classifying relapsing refractory (R/R) vs non-(R/R) patients.Methods:We retrospectively included 85 patients (male:female = 52:33; median age35 years, range 19–74). LIFEx (www.lifexsoft.org) was used for [18F]FDG-PET/CTsegmentation and feature extraction. Features werea-prioriselected if they werehighly correlated or uncorrelated to the volume. Principal component analysis-transformed features were used to build the fingerprints that were tested to assesslesions’similarity, using thesilhouette. For intra-patient similarity analysis, we usedpatients having multiple lesions only. To classify patients as non-R/R and R/R, thefingerprint considering one single lesion (fingerprint_One) and all lesions(fingerprint_All) was tested using Random Undersampling Boosting of Tree Ensemble(RUBTE).Results:HL fingerprints included up to 15 features. Intra-patient lesion similarityanalysis resulted in mean/median silhouette values below 0.5 (low similarityespecially in the non-R/R group). In the test set, the fingerprint_One classificationaccuracy was 62% (78% sensitivity and 53% specificity); the classification by RUBTEusing fingerprint_All resulted in 82% accuracy (70% sensitivity and 88% specificity).Conclusions:Lesion similarity analysis was developed, and it allowed to demonstratethat HL lesions were not homogeneous within patients in terms of radiomics signature.Therefore, a random target lesion selection should not be adopted for radiomicsapplications. Moreover, the classifier to predict R/R vs non-R/R performed the bestwhen all the lesions were used.