Statistical analysis
The statistical software packages SPSS version 22.0 (Chicago, IL, USA) and GraphPad Prism version 5.00 for Windows (San Diego California USA) were used to analyze the data. To determine the value of interim and post-treatment PET/CT in the prediction of the outcomes of pediatric and adolescent HL patients, we calculated the sensitivity, specificity, positive likelihood (+LH), negative likelihood (-LH), area under the curve (AUC), positive predictive value (PPV), negative predictive value (NPV) and accuracy for the IHPC, DC-3, and DC-4 models. Survival curves were estimated using the Kaplan-Meier method with Rothman’s 95% confidence intervals (CIs) and log-rank tests. PFS was defined as the interval from the diagnosis to the first clinical or radiological progression or the date of the last follow-up visit for those without events. Factors with A P value of less than 0.05 were introduced into multivariate analysis, performed by the Cox proportional hazard model using the forward procedure. A P value of less than 0.05 was considered statistically significant.