INTRODUCTION
Hodgkin lymphoma (HL) accounts for 6%~8% of all childhood malignancies and 15%–20% of all childhood lymphomas1. 18F-Fluorodeoxyglucose positron-emission tomography-computed tomography (18F-FDG-PET/CT) is widely used for staging, response evaluation, and surveillance in lymphoma2. The outcomes of pediatric and adolescent patients with HL have improved since the application of PET/CT-based, response-adapted therapy3-5. In a study by the Children’s Oncology Group, the cumulative incidence of relapse in pediatric and adolescent HL patients was 17%, and the 5-year progression-free survival (PFS) rate was 83%6. Interim PET/CT has been used to identify patients with an inadequate response, and has been demonstrated to be an accurate predictor of prognosis in adult lymphoma. Post-treatment PET/CT is also highly useful for outcome prediction, with high negative predictive values (NPVs) of 94%–100% and positive predictive values (PPVs) of 91%–92% for a PFS ≥ 2 years in adult HL patients treated with the ABVD (doxorubicin, bleomycin, vinblastine, dacarbazine) regimen7-10. However, similar studies concerning interim and post-treatment PET/CT in pediatric and adolescent HL patients are limited. A few retrospective studies with small sample sizes have reported NPVs of 90%–100% but PPVs of only 20%–40%11, 12.
In 2007, the Imaging Subcommittee of the International Harmonization Project in Lymphoma recommended the International Harmonization Project Criteria (IHPC) for post-treatment assessment; however, the IHPC do not relate specifically to interim treatment, and their inter-observer variability has not been assessed13,14. In 2009, the Deauville Criteria (DC) were proposed for the visual evaluation of interim PET scans based on the application of a 5-point scale; these criteria showed good diagnostic accuracy and inter-observer concordance in patients with HL and non-Hodgkin lymphoma15, 16. However, the use of the DC relies on consistency in scanning conditions over serial scans, scan acquisition, and quality control of imaging equipment17. Moreover, it is unclear whether a DC score of 3 should be considered as positive, and the threshold of FDG uptake chosen to define response is controversial. Although PET/CT has demonstrated similar diagnostic performance and clinical utility in pediatric and adolescent HL, experience with this technique is still limited15,18. Therefore, the true effectiveness of the IHPC and DC remains unclear, and the optimal criteria for defining treatment response in pediatric and adolescent HL patients remain to be determined. Hence, this study reviewed the baseline, interim, and post-treatment PET/CT scan data of pediatric and adolescent patients with HL. The aims of this study (1) to determine the diagnostic performance of interim and post-treatment PET/CT when applying the IHPC and DC for the prediction of clinical outcomes in pediatric and adolescent HL patients, and (2) to identify which criteria better predict the risk of progression in this patient population.