Extracorporeal photopheresis (ECP) is one of the most used and established therapies for steroid-refractory graft versus host disease (GvHD), with a good effect to side effect profile. In this review we present a summary of present literature and provide evidence-based treatment guidelines for ECP in GvHD. The guidelines constitute a consensus statement formed by the Nordic ECP Quality Group representing
all ECP centres in the Nordic countries, and aims to facilitate harmonization and evidence based practise. In developing the guidelines, we firstly conducted a thorough literature search of original articles and existing guidelines. In total, we identified 26 studies for ECP use in acute GvHD and 36 in chronic GvHD. The studies were generally small, retrospective and heterogeneous regarding patient characteristics, treatment schedule and outcome assessment. In general, a majority of patients achieved partial response or better, but response rates varied by the organs affected. Head to head comparisons to other treatment modalities were lacking. Overall, we consider the quality of evidence to be low-moderate (GRADE) and encourage future prospective multi-armed trials to strengthen the present recommendations. However, despite limitations in evidence strength, standardized treatment schedules and regular follow-up are imperative to ensure the best possible patient outcome.