2.3. Follow-up
Progression (PD) before achieving complete remission (CR), relapse after
CR, secondary cancer or Langenhans cell histiocytosis (LCH), and death
due to any cause were evaluated as events. The criterion of PD, CR and
stable disease (SD) was in consistence with the International Pediatric
NHL Response Criteria.26 OS time was calculated from
the time of initial diagnosis to death; event-free survival (EFS) time
was from the time of initial diagnosis to the first event. Patients who
had not died or experienced other events at final analysis were censored
at the last follow-up in May 2020.