Fitness-adapted, Pembrolizumab-based Therapy for Untreated Classical Hodgkin Lymphoma Patients 60 Years of Age and Above

This is a multi-center, open-label phase II study to assess the efficacy of a novel fitness-adapted regimen in previously untreated older patients with classical Hodgkin lymphoma. All participants will receive up to a total of 8 cycles of pembrolizumab (Q6 week dosing). The first cycle of pembrolizumab will be administered in combination with brentuximab vedotin (BV) ("lead-in treatment"). Following lead-in treatment, all participants will undergo interim PET/CT (iPET) as well as fitness testing to help inform participant level of fitness for subsequent lymphoma-directed therapies. Participants deemed "Frail" by this assessment will continue 3 additional 6 week cycles of concurrent pembrolizumab and BV ("induction therapy", each cycle is 42 days), then continue single-agent pembrolizumab to complete up to 4 additional cycles (i.e., 8 total) of therapy ("consolidation and maintenance therapy", Frail cohort). Two additional BV doses will be given as consolidation, at days 1 and 22 of pembrolizumab cycle 5. Those deemed "fit" after lead-in therapy (Fit cohort) will continue pembrolizumab and switch from BV to concurrently-administered combination chemotherapy using doxorubicin (A), vinblastine (V), and dacarbazine (D) for a total of 4 planned AVD cycles (3, 6-week pembrolizumab cycles, "induction therapy"). Chemotherapy drugs will be given at standard doses as in ABVD (no bleomycin will be given in this study) on days 1 and 15 of each 28-day cycle (C1AVD), and pembrolizumab dosing will remain every 42 days. Following end-induction PET/CT, pembrolizumab will continue every 42 days for up to 4 cycles in the consolidation/maintenance phase. Two additional BV doses will be given as consolidation, at days 1 and 22 of pembrolizumab cycle 5. Participants deemed "unfit" after lead-in therapy and by fitness assessment will continue pembrolizumab and switch from BV to concurrently administered combination chemotherapy termed "mini-avd" as induction therapy. Mini-avd consists of lower doses of conventional AVD chemotherapy (doxorubicin, vinblastine and dacarbazine) and will be administered for on days 1 and 15 of a 28 day cycle for 4 planned cycles. Pembrolizumab will continue every 42 days. Following end-induction PET/CT, pembrolizumab will continue every 42 days for up to 4 cycles in the consolidation/maintenance phase. Two additional BV doses will be given as consolidation, at days 1 and 22 of pembrolizumab cycle 5.