This study enrolls newly diagnosed unfavorable stage II /stage III-IV classical Hodgkin lymphoma patients. All participants receive 2 cycles ABVD induction chemotherapy, then stratified by interim PET-CT Deauville score for differentiated treatment: standard ABVD for DS1-3, AVD plus Sintilimab for DS4, salvage chemotherapy plus autologous stem cell transplant for DS5. The primary goal is to assess 2-year progression-free survival and compare long-term survival and toxicities across subgroups, to verify whether Sintilimab addition can avoid high-dose chemo-radiotherapy for DS4 patients.