Baseline PET features to predict prognosis in primary mediastinal B cell lymphoma: a comparative analysis of different methods for measuring baseline metabolic tumour volume

Abstract

Purpose This study assessed the performance of four different methods for the estimation of metabolic tumour volume (MTV) in primary mediastinal B cell lymphoma (PMBCL). Method MTV was estimated using either a region growing automatic software program (RG) or a fixed threshold (FT) segmentation algorithm with the three most common cutoffs proposed in the literature (i.e., 25% and 41% of the SUVmax and SUV value ≥2.5). We compared these four methods using phantoms that simulated different setups of the main imaging characteristics of PMBCL (volume, shape, 18-FDG uptake and intra-lesion distribution) and assessed their performance in 103 PMBCL patients enrolled in the International Extranodal Lymphoma Study Group-26 (IELSG-26) study. Results There was good correlation between MTV values estimated in vitro and in vivo using the different methods. The 25% FT cutoff (FT25%) provided the most accurate MTV evaluation in the phantoms. The cutoff at SUV 2.5 (FT2.5) resulted in MTV overestimation that particularly increased with high SUV values. The 41% cutoff (FT41%) showed MTV underestimation that was more evident when there were high levels of heterogeneity in tracer distribution. Shape of the lesion did not affect MTV computation. The RG algorithm provided a systematic slight MTV underestimation without significant changes due to lesion characteristics. We observed analogous trends for the MTV estimation in patients, with very different derived thresholds for the four methods. Optimal cutoffs for predicting progression-free survival (PFS) ranged from 213 to 831 ml. All methods predicted PFS with similar negative predictive values (94-95%) but different positive predictive values (23-45%). Conclusions The different methods result in significantly different MTV cutoff values. All allow risk stratification in PMBCL, but FT25% showed the best capacity to predict disease progression in the patient cohort and provided the best accuracy in the phantom model.

Prognostic models integrating quantitative parameters from baseline and interim positron emission computed tomography in patients with diffuse large B‐cell lymphoma: post‐hoc analysis from the SAKK38/07 clinical trial

“…47 In this study, we use a segmentation method with a fixed-threshold at SUV ¼ 2.5 that has analogous accuracy and offers a better tumor coverage in comparison with the widely used percentage threshold at 41% of SUV max . 45,47,53 The median MTV in our cohort appears lower than in other series using the same fixed-threshold methodology 47 which may be easily explained by a relatively larger number of patient with early stage in our study.…”

SAKK38/07 study: integration of baseline metabolic heterogeneity and metabolic tumor volume in DLBCL prognostic model

“…Different procedures and a wide range of threshold levels have been proposed to calculate MTV. 35,43,49 Moreover, the prognostic effect of MTV has been estimated using cut-points that are heavily cohort-dependent, being generated by ROC analysis of small series. In this study, we chose to use a segmentation method with a fixed-threshold at SUV 5 2.5 43 that, compared with the widely used percentage threshold at 41% of SUVmax, maintains a similar accuracy and offers better tumor coverage, 41 particularly in lesions with heterogeneous FDG uptake distribution.…”

“…In this study, we chose to use a segmentation method with a fixed-threshold at SUV 5 2.5 43 that, compared with the widely used percentage threshold at 41% of SUVmax, maintains a similar accuracy and offers better tumor coverage, 41 particularly in lesions with heterogeneous FDG uptake distribution. 49 Although the lack of standardization endangers the reproducibility of the results obtained in retrospective studies, there is increasing evidence of the prognostic value of quantitative parameters obtained from 18FDG-PET/CT in patients with different non-Hodgkin lymphoma subtypes. 17,26,28,50,51 We sought to use the quantitative parameters from PET scans to discriminate patient with different outcomes.…”

Correlation of texture feature analysis with bone marrow infiltration in initial staging of patients with lymphoma using 18F-fluorodeoxyglucose positron emission tomography combined with computed tomography

“…A recent report looking at the differences that arise from tumour volume segmentation has shown that low MTV had a significantly longer progression-free survival and overall survival compared to patients with high MTV. These findings were obtained regardless of the segmentation methods used [29].…”