686 Targeted immunotherapy and checkpoint blockade in children, adolescents, and young adults with lymphoma: RADICAL hodgkin cohort af Matthew Barth, Mitchell S Cairo, Megan S Lim, Lauren Harrison, Chitti Moorthy, Saro Armenian, Kayleigh Klose, Jessica C Hochberg, Jaclyn Baso, Ana C Xavier, Anthony N Audino, Rodney Miles, Samir Kahwash, Stephan D Voss, Suzanne Braniecki, Matthew Ehrhardt, Arvind Budhram, Ariel Stonberg, Stanton Goldman