Patient characteristics
A total of 147 patients completed the post-treatment PET/CT scan, including 104 (70.7%) boys and 43 (29.3%) girls. Their median age was 14 years (range, 2–21 years). There were 3.4% (5/147) stageⅠpatients, 57.1% (84/147) stageⅡpatients, 21.1% (31/147) stage Ⅲ patients, 18.4% (27/147) stage Ⅳ patients, respectively. Risk stratification placed 44.2% (65/147) of the patients in the low-risk group, 10.9% (16/147) in the middle-risk group, and 44.9% (66/147) in the high-risk group. All patients achieved CR after first-line chemotherapy with a median course of 6 cycles (range, 4–14 cycles). Radiotherapy was performed in 66.7% (98/147) of the patients. The median follow-up duration was 48 months (range, 8–117 months), during which time, 15 patients experienced relapse, and 1 patient died of relapse. 89/147 patients completed interim PET/CT after 2 cycles of chemotherapy. The characteristics of the patients with only post-treatment PET/CT scans and those with both interim and post-treatment PET/CT scans are summarized in Table 1.