Posttreatment PET/CT Rather Than Interim PET/CT Using Deauville Criteria Predicts Outcome in Pediatric Hodgkin Lymphoma: A Prospective Study Comparing PET/CT with Conventional Imaging

Abstract

Data about significance of ¹⁸F-FDG positron emission tomography (PET) at interim assessment and end of treatment in pediatric Hodgkin lymphoma (HL) are limited. Methods: Patients (≤18 years) with HL were prospectively evaluated with contrast-enhanced computed tomography (CECT) and PET combined with low-dose CT(PET-CT) at baseline, post 2 cycles of chemotherapy and post completion of treatment. Revised international working group criteria (RIW) and Deauville (DA) five point-scale for response assessment by PET-CT were used. All patients received ABVD chemotherapy along with involved field radiotherapy (25 Gy) for early stage (IA, IB and IIA) and advanced stage (IIB-IV) with bulky disease. Results: Of the 57 enrolled patients, median follow-up was 81.6 months (range: 11-97.5 months). Treatment decisions were based on CECT. At baseline, PET-CT vs CECT identified 67 more disease sites; 23 patients (40.3%) were upstaged and of them in 9 patients (39%) upstaging would have affected treatment decision; notably none of these patients relapsed. Specificity of interim PET-CT based on RIW (61.5%) and DA (91.4%) criteria for predicting relapse was higher than CECT (40.3%) (P = 0.03 and p≤0.0001 respectively). Event free survival (EFS) based on interim PET-CT response (positive vs. negative scan: 93.3±4.1 vs. 89.6±3.8; P = 0.44). Specificity of post-treatment PET-CT (DA) was 95.7% vs. 76.4% by CECT (P = 0.006). Post-treatment PET-CT (DA) showed significantly inferior overall survival (OS) in patients with positive scan vs. negative scan (66.4±22.5 vs. 94.5±2.0, P = 0.029). Conclusion: Interim PET-CT has better specificity and use of DA criteria further improves it. Escalation of therapy based on interim PET in pediatric HL needs further conclusive evidence to justify its use. Post-treatment PET-CT (DA) predicts OS and has better specificity in comparison to conventional imaging.