Background: The National Cancer Institute defines adolescent/young adult as 15-39y. Guidelines from ASCO and Friends of Cancer Research call for including children ≥12y on late phase trials spanning children and adults. We examined whether, in children and adolescents receiving response-based therapy for Hodgkin lymphoma (HL), age ≥12y would define a group with inferior outcomes compared to younger patients. Methods: This was a pooled analysis of individual patient-level data from three COG Phase 3 trials for intermediate, low, high-risk HL (AHOD0031, AHOD0431, AHOD0831). 5-yr event free survival (EFS) and overall survival (OS) by age were estimated via Kaplan Meier method. Cox regression models examined the influence of age on EFS and OS, adjusted for race/ethnicity, sex, insurance, histology, Ann Arbor stage, B symptoms, bulk, study, and radiation therapy (RT). Results: We included 2071 of 2155 patients, 1-21y enrolled from 2002 -2012. Mean age at diagnosis was 14.6y (±3.5) with 54% ≥15y (N = 1121) and 81% ≥12y (N = 1684). At median follow-up of 6.9 years, patients < 15y had statistically significantly better EFS ( < 15y: 85% vs. ≥15y: 80%, p = 0.02). A difference in EFS was noted in those < 12y vs. ≥12y (87% vs. 81%, p = 0.0503). OS was significantly better in patients < 15y vs. ≥15y (98% vs. 95%, p = 0.006), but did not differ in < 12y vs. ≥12y (99% vs. 97%, p = 0.136). Cumulative incidence of second malignant neoplasm did not differ by age category. In multivariable models, older age was an independent predictor of treatment failure in both age categories (Table). Conclusions: With contemporary, response-based therapy on COG trials, adolescents ≥12 and ≥15y had worse EFS than younger groups. This suggests that children ≥12y may benefit from therapy escalation and inclusion in late phase trials of novel agents incorporating antibody drug conjugates or checkpoint inhibitors.

HR: hazard ratio; 95%CI: 95% confidence interval; R: reference group