The genomic and clinical consequences of replacing procarbazine with dacarbazine in escalated BEACOPP for Hodgkin lymphoma: a retrospective, observational study

Procarbazine-containing chemotherapy regimens are associated with cytopenias and infertility, suggesting stem-cell toxicity. When treating Hodgkin lymphoma, procarbazine in escalated-dose bleomycin–etoposide–doxorubicin–cyclophosphamide–vincristine–procarbazine–prednisolone (eBEACOPP) is increasingly replaced with dacarbazine (eBEACOPDac) to reduce toxicity. We aimed to investigate the impact of this drug substitution on the mutation burden in stem cells, patient survival, and toxicity. In this two-part retrospective, observational study, we first compared mutational landscapes in haematopoietic stem and progenitor cells (HSPCs) from patients with advanced-stage Hodgkin lymphoma in remission for at least 6 months who had been treated with eBEACOPDac (eBEACOPDac cohort), eBEACOPP (real-world eBEACOPP cohort), or doxorubicin–bleomycin–vinblastine–dacarbazine (ABVD); in buccal DNA from five children of a female patient with classical Hodgkin lymphoma treated with eBEACOPP before conceiving the third child; in sperm DNA from a patient with mild oligospermia treated with eBEACOPP; and in caecal adenocarcinoma and healthy colon tissue from a survivor of Hodgkin lymphoma treated with chlorambucil–vinblastine–procarbazine–prednisolone. For the second part, we analysed efficacy and toxicity data from adult patients (aged >16 years) treated with first-line eBEACOPDac (eBEACOPDac cohort) at 25 centres across UK, Ireland, and France; efficacy was compared with the German HD18 eBEACOPP trial data and toxicity with a UK real-world dataset. Participants in the German HD18 and UK real-world datasets were adults (aged >16 years) with previously untreated Hodgkin lymphoma, treated with first-line eBEACOPP. We had two co-primary objectives: to define the comparative stem-cell mutation burden and mutational signatures after treatment with or without procarbazine-containing chemotherapy (first study part); and to determine progression-free survival of patients with Hodgkin lymphoma treated with eBEACOPP or eBEACOPDac (second study part). Secondary objectives included overall survival and explored differences in specific toxicity outcomes, including transfusion requirements and measures of reproductive health (second study part). In the first part of the study (mutational analysis), patients treated with eBEACOPP (n=5) exhibited a higher burden of point mutations in HSPCs compared with those treated with eBEACOPDac (n=4) or ABVD (n=3; excess mutations 1150 [95% CI 934–1366] vs