S203: ABSCOPAL EFFECT OF RADIOTHERAPY AND NIVOLUMAB IN RELAPSED OR REFRACTORY HODGKIN LYMPHOMA: PRE-PLANNED INTERIM ANALYSIS OF THE INTERNATIONAL GHSG PHASE II AERN TRIAL. (23rd June 2022) - Bröckelmann, P.; Bühnen, I.; Zijlstra, J.; Fossa, A.; Meissner, J.; Mathas, S.; Rosenbrock, J.; Kobe, C.; Fuchs, M.; Plütschow, A.; Marnitz, S.; Borchmann, P.; et al.