Additional Study Information: This Phase III trial investigates if the incorporation of immunotherapy will improve progression-free survival (PFS) and maintain overall survival (OS) while simultaneously minimizing long-term morbidity and treatment-related mortality by reducing exposure to radiotherapy and high cumulative chemotherapy doses. The study will enroll patients ages 5 to 60 years with newly diagnosed early-stage cHL and will investigate the targeted CD30-antibody drug conjugate, Brentuximab Vedotin (Bv), with PD-1 blockade (nivolumab) compared with a standard chemotherapy regimen, with or without radiotherapy.