Pretherapeutic FDG-PET total metabolic tumor volume predicts response to induction therapy in pediatric Hodgkin’s lymphoma

Standardized treatment in pediatric patients with Hodgkin’s lymphoma (HL) follows risk stratification by tumor stage, erythrocyte sedimentation rate and tumor bulk. We aimed to identify quantitative parameters from pretherapeutic FDG-PET to assist prediction of response to induction chemotherapy.

Methodik/Methods:

Retrospective analysis in 50 children with HL (f:18; m:32; median age, 14.8 [4-18] a) consecutively treated according to EuroNet-PHL-C1 (n=42) or -C2 treatment protocol (n=8). Total metabolic tumor volume (MTV) in pretherapeutic FDG-PET was defined using a semi-automated, background adapted threshold. Metabolic (SUVmax/mean/peak, total lesion glycolysis [MTV*SUVmean]) and heterogeneity parameters (asphericity [ASP], entropy, contrast, local homogeneity, energy, and cumulative SUV-volume histograms) were derived. Early response assessment (ERA) was performed after 2 cycles of induction chemotherapy according to treatment protocol and verified by reference rating. Prediction of inadequate response (IR) in ERA was based on ROC analysis separated by stage 1/2 (1 and 26 patients) and stage 3/4 disease (7 and 16 patients) or treatment group/level (TG/TL) 1 to 3.

Ergebnisse/Results:

IR was seen in 28/50 patients (TG/TL1, 6/12 patients; TG/TL2, 10/17; TG/TL3, 12/21). Among all PET parameters, MTV best predicted IR; ASP was the best heterogeneity parameter. AUC of MTV was 0.84 (95%-confidence interval, 0.69-0.99) in stage 1/2 and 0.86 (0.7-1.0) in stage 3/4. In patients of TG/TL1, AUC of MTV was 0.92 (0.74-1.0); in TG/TL2 0.71 (0.44-0.99), and in TG/TL3 0.85 (0.69-1.0). Patients with high vs. low MTV had IR in 86 vs. 0% in TG/TL1, 80 vs. 29% in TG/TL2, and 90 vs. 27% in TG/TL3 (cut-off, >80 ml, >160 ml, >410 ml).

Schlussfolgerungen/Conclusions:

In this explorative study, high total MTV best predicted inadequate response to induction therapy in pediatric HL of all pretherapeutic FDG-PET parameters – in both low and high tumor stages as well as the 3 different TG/TL.