Background: In paediatric Hodgkin lymphoma (HL), total metabolic tumour volume (MTV) is an established prognostic biomarker, yet published cut-offs apply a single absolute threshold regardless of body size. A 400 mL tumour represents greater relative burden in a 7-year-old (BSA 1.0 m2) than a 17-year-old (BSA 2.0 m2). We investigated whether normalising MTV by body surface area (MTV/BSA) improves prognostic performance and reclassifies smaller children into higher risk groups.
Methods: Sixty-one paediatric HL patients (BC Children’s Hospital, 2014–2023; median age 15.6 y, range 7.2–19.5) were included. MTV and TLG were extracted from baseline FDG-PET/CT using an IBSI-compliant pipeline. BSA was available in 55/61 patients. Normalised metrics (MTV/BSA, TLG/BSA) were compared with raw values using ROC analysis, Youden-index cut-offs, Cox regression (HR per 1 SD), and Kaplan–Meier analysis. Reclassification analysis identified patients changing risk categories when MTV/BSA replaced raw MTV. Endpoint: PFS (13/61 events [21%]; median follow-up 4.7 years).
Results: BSA correlated weakly but significantly with raw MTV (Spearman r = 0.33; p = 0.026). Despite this, MTV/BSA did not improve prognostic performance (AUC 0.673 vs 0.710; HR 1.31; p = 0.301; see Table 1). TLG was the strongest predictor (AUC 0.746; HR 1.75; p = 0.014) and was not improved by normalisation (TLG/BSA: AUC 0.710; p = 0.081). BSA alone showed moderate prognostic value (AUC 0.707; p = 0.164); progressors had higher median BSA than non-progressors (1.89 vs 1.73 m2). Reclassification analysis (n = 45) showed 3/45 patients (7%) changed risk group as derived statistically: 1 upstaged (MTV 405 mL, BSA 1.30 m2, age 16.6 y; no progression) and 2 downstaged (BSA ≥2.44 m2; no progression). No progressing patient was reclassified.
Conclusion: In this adolescent-predominant cohort (age 7–19 y), BSA normalisation of MTV did not improve prognostic discrimination and produced clinically minimal reclassification (3/45 patients; no progressor reclassified). Raw TLG outperformed all normalised metrics. These findings suggest that for the typical paediatric HL age range, absolute volumetric burden is an adequate prognostic surrogate without body-size correction. However, a reclassification signal was observed in one patient with small habitus (BSA 1.30 m2), supporting prospective evaluation in young children (≤ 10 years) with wider BSA variation.
Claire Gowdy, Caron Strahlendorf, Andrea C. Lo, Yvonne Mbithi, Carlos Uribe, Arman Rahmim, Fereshteh Yousefirizi