Pembrolizumab Followed by Chemotherapy for the Treatment of Patients With Classical Hodgkin Lymphoma

Inclusion Criteria: * Patients must have a histologically confirmed diagnosis of Ann Arbor Stage III or IV classic Hodgkin lymphoma (cHL) or Ann Arbor Stage I and Stage II classic Hodgkin lymphoma with at least one unfavorable risk factor by National Comprehensive Cancer Network (NCCN) criteria. NCCN Unfavorable Factors include bulky disease defined as: * A mass \>10 cm disease in any dimension or * Mediastinal mass ratio greater than one third defined as maximum width of mediastinal ass/intrathoracic diameter at T5-6 * B symptoms * Erythrocyte sedimentation rate (ESR) ≥ 50 * And \>3 sites of disease * Patients must have measurable fludeoxyglucose (FDG)-avid disease by Lugano 2014 response criteria * Patients must have previously untreated disease * Patients must be age ≥ 18 years * Patients must exhibit an Eastern Cooperative Oncology Group (ECOG) performance status of 0-1 per evaluation performed within 7 days prior to the date of the first dose of study intervention * Leukocytes (WBC) ≥ 3,000/mcL unless attributed to neoplastic involvement of the bone marrow * Platelet transfusions are acceptable prior to treatment to achieve the above numbers, however growth factors are not allowed within 14 days of registration * No lower limit if cytopenia is related to bone marrow involvement. * Absolute neutrophil count (ANC) ≥ 500/mcL unless attributed to neoplastic involvement of the bone marrow * Platelet transfusions are acceptable prior to treatment to achieve th…