Early and late-onset veno-occlusive disease/sinusoidal syndrome post allogeneic stem cell transplantation - a real-world UK experience.

Classical veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is a serious complication post allogeneic hematopoietic stem cell transplantation (HSCT). Before the recently revised EBMT criteria, the Baltimore and modified Seattle criteria failed to recognize the syndrome of late-onset VOD. We present real-world experience from a large UK transplant center reporting on VOD/SOS in consecutive HSCT adult patients (n = 530), transplanted for hematological cancers. We identified 27 patients treated with Defibrotide for VOD/SOS diagnosis, where detailed data were available for final analysis. Using standard definitions including EBMT criteria, around 30% (n = 8/27) of cases classified as late-onset VOD presenting at median of 46 (22-93) days but with D100 survival (63% vs 58%, Log-rank; P = 0.81) comparable to classical VOD. Hazard ratio for D100 mortality was 2.82 (95% CI: 1.74-4.56, P < .001, Gray test) with all VOD/SOS events. Twenty percent (n = 2/8) of late-onset VOD patients were anicteric and 42% (n = 8) classical VOD patients presented with refractory thrombocytopenia, while less than half met EBMT criteria for classical VOD in adults, highlighting gaps in real-world diagnostic limitations using EBMT criteria. However, challenges remain about underrecognition and difficulties related to early defibrotide access for treatment of late-onset VOD in current treatment guidelines. Our report strongly supports early Defibrotide for the treatment of severe VOD/SOS in adults regardless of time of onset.