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.