1300P - Use of checkpoint inhibitors (CPI) in allogeneic stem cell transplant recipients: An institutional experience and a systemic review of the literature

With the expanding use of CPI in different types of cancer, we have been challenged with the lack of safety and efficacy data of CPI post allogeneic stem cell therapy (SCT). We systematically reviewed our institutional databases through March 2018 and identified patients (pts) who received CPI for treatment of cancer after allogeneic SCT. In addition, we systematically reviewed the literature through August 2018 to identify studies reporting use of CPIs post-allogeneic SCT. We evaluated the prevalence of graft vs host disease (GVHD), immune-related adverse events (irAEs), tumor response, and mortality after CPI. A total of 38 pts were identified (10 from institutional databases & 28 from literature). The median age was 37.5years (range 10–68yrs). The most commonly used CPI was anti-PD1 84 %. Cancer types included hematologic malignancies (n=36); primarily Hodgkin lymphoma in 58%, and solid tumors (n=2). Median time to CPI initiation post SCT was 1.6years (range 0.92–32 yrs). More than half of pts (59 %) were maintained on immunosuppressive agents: brentuximab vedotin, cyclophosphamide, and low dose prednisone at CPI initiation. GVHD occurred in 34.2 % (n=13); nine were specified having acute GVHD (82%). The median time from initiation of CPI to GVHD was 14 days (range 5-21 days). In most pts, GVH was treated with steroids. Two thirds of pts achieved complete or partial tumor remission (ORR 66%), while 28% had disease progression. In pts who developed GVHD the ORR was 91.2%. Interestingly, of the 25 pts who were reported to have no GVHD, 10 had irAEs. There were total of 34% of death (n=13), including 5% only (n=2) were attributed to GVHD, while the remaining were secondary to either progression of disease, CPI irAE’s (Pneumonitis, Myocarditis), and other causes. The use of CPI post-SCT has a significant anti-tumor response, but it was associated with an increased risk of acute GVHD. Prospective studies in this population (CPI post-SCT) with longitudinal on treatment biopsies are needed to understand the differences between allo-immunity, tumor immunity and auto-immunity (irAE). Adi Diab. Has not received any funding. All authors have declared no conflicts of interest.