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Safety of Allogeneic Stem Cell Transplantation after PD-1 Blockade for Patients with Relapsed/Refractory Classical Hodgkin Lymphoma: Focus on Immune-Related Adverse Events


 Introduction:
 Allogeneic hematopoietic stem cells transplantation (allo-HSCT) is a potentially curative option for patients with relapsed and refractory Hodgkin lymphoma (rrHL). However, there is a question of applicability of allo-HSCT for patients previously treated with immune checkpoint inhibitors (ICIs). Initial reports indicate that allo-HSCT in this setting may be associated with increased risk of early transplant-related toxicity, graft versus host disease (GVHD), immune-related adverse events. But subsequently some studies demonstrated acceptable rates of both acute GVHD (aGVHD) and chronic GVHD (cGVHD) after prophylaxis with posttransplantation cyclophosphamide (PTCy). The aim of this study was to define safety and toxicity of allo-HSCT after ICIs for patients with rrHL.
 Patients and methods:
 We conducted a retrospective analysis of allo-HSCT results in 23 adult patients with rrHL performed between 2017 and 2019 in RM Gorbacheva Research Institute, Pavlov University. All patients were treated with ICIs before the transplantation (single-agent nivolumab, n=13; nivolumab and brentuximab vedotin, n=5; nivolumab and chemotherapy, n=5). The median time from the last dose of ICIs to allo-HSCT was 83 days (range, 50-350 days) and the median number of cycles was 20 (range, 6-32). Objective response to PD-1 therapy before allo-HSCT was documented in 15 patients (65%) including CR (n=9, 39%) and PR (n=6, 26%). Five patients (22%) had stable disease/disease progression and 3 patients (13%) were transplanted in indeterminate response according to LYRIC criteria. Three (13%) patients had matched HLA-related siblings, 12 patients (52%) had unrelated donors and 8 patients (35%) had haploidentical donors. All patients received reduced-intensity conditioning regimen (fludarabine 30 mg/m2, bendamustine 130 mg /m2 per day for 3 days (FluBe)) and PTCy-based GvHD prophylaxis. Bone marrow and peripheral blood stem cells was the graft source in 14 (61%) and 9 patients (39%), respectively. All analyses were performed using R 3.6.1 software.
 Results: At the time of analysis, median follow-up was 14 months (range, 1-26). Engraftment rate was 87%. Two patients had primary graft failure and there was 1 early death due to severe cytokine release syndrome after haploidentical HSCT. The 1-year OS and EFS were 83% (95% CI, 58-93) and 74% (95% CI, 49-87) respectively, whereas the 1-year cumulative incidences of relapse and NRM were 13% (95% CI, 5-39) and 13% (95% CI, 5-38) respectively.Out of the 20 patients with engraftment 15 patients developed acute GVHD including severe (grade III-IV) in 9 patients. All patients had skin aGVHD (stages 1, 2, and 3), 3 patients had gastrointestinal GVHD (stages 2, 3, and 4) and 2 patients had liver GVHD (stages 1 and 2). Four patients with steroid-refractory aGVHD received single-agent ruxolitinib (n=2) or combination of ruxolitinib with extracorporeal photopheresis (ECP) and steroids (n=2). All patients achieved complete response. Ten patients had chronic GVHD including 6 patients with moderate or severe disease. Most commonly skin (90%), mucosa (60%), gastrointestinal tract (30%), liver (20%), lung (10%) and eyes (20%) were involved. Four patients with steroid-refractory cGVHD achieved CR receiving combined immunosuppressive therapy (ruxolitinib and steroids, n=2; combination of steroids, cyclosporine A and ECP, n=2). One patient with severe skin cGVHD (score 3) achieved PR on combination of steroids and ECP, another patient with a severe refractory cGVHD (skin score 3, mucosa score 2 and lungs score 1) achieved stabilization only with third line of therapy (combination of ruxolitinib and imatinib). No cases of GVHD-related mortality were observed. There were no other immune-related adverse events.
 Conclusions: Our study showed the trend to higher incidence of aGVHD and cGHVD including steroid refractory form after ICIs, however this did not lead to GVHD-related mortality. Introduction of target agents for srGVHD might ameliorate GVHD-related mortality and morbidity in rrHL patients after ICIs. The optimal timing of allo-HSCT and regimen of GVHD prophylaxis are likely to be important in the successful outcome of the transplantation.
 
 
 No relevant conflicts of interest to declare.
