Pembrolizumab and Brentuximab Vedotin vs GDP and Stem Cell Transplant for Relapsed/Refractory Hodgkin Lymphoma

Inclusion Criteria: * History of classic Hodgkin lymphoma by histopathology and now have relapsed or refractory disease after anthracycline-containing chemotherapy and eligible for high dose chemotherapy and autologous stem cell transplant * 18 years of age or greater * ECOG performance status 0-1 * Clinically and/or radiologically measurable disease as per the Lugano 2014 classification * Life expectancy \> 90 days * Absolute neutrophils ≥1.0 x 10\^9/L; Platelets ≥75 x 10\^9/L; Hemoglobin ≥80 g/L: Bilirubin ≤1.50 x UNL; AST and ALT ≤2.50 x UNL; Serum creatinine \<1.55 x UNL or Creatinine clearance ≥30 mL/min * Participant is able (i.e. sufficiently fluent) and willing to complete the quality of life questionnaires and/or health utility in either English or French * Participant consent must be appropriately obtained in accordance with applicable local and regulatory requirements. Each participant must sign a consent form prior to enrollment in the trial to document their willingness to participate. * Participants must be accessible for treatment and follow-up. * In accordance with CCTG policy, protocol treatment is to begin within 2 working days of participant enrollment * Women/men of childbearing potential must have agreed to use a highly effective contraceptive method during the study plus approximately 6 months after treatment completion * All patients must have a tumour block from their primary diagnostic biopsy and relapse/refractory biopsy if available and the centre/…