Acute and chronic graft-versus-host disease (GVHD) remain major obstacles for successful allogeneic hematopoietic cell transplantation. Extracorporeal photopheresis (ECP) modulates immune cells, such as alloreactive T cells and dendritic cells, and improves GVHD target organ function(s) in steroid-refractory GVHD patients. We performed a systematic review to evaluate the totality of evidence regarding the efficacy of ECP for treatment of acute and chronic steroid-refractory or steroid-dependent GVHD. Nine studies, including 1 randomized controlled trial, met inclusion criteria, with a total of 323 subjects. In pooled analyses, overall response rates (ORR) were .69 (95% confidence interval [CI], .34 to .95) and .64 (95% CI, .47 to .79) for acute and chronic GVHD, respectively. In acute GVHD organ-specific responses, ECP resulted in the highest ORR for cutaneous, with .84 (95% CI, .75 to .92), followed by gastrointestinal with .65 (95% CI, .52 to .78). Similar response rates were seen in chronic GVHD involving the skin and gastrointestinal tract. Conversely, ORR for chronic GVHD involving the lungs was only .15 (95% CI, 0 to .5). In chronic GVHD, grades 3 to 4 adverse events were reported at .38 (95% CI, .06 to .78). ECP-related mortality rates were extremely low. Rates of immunosuppression discontinuation were .55 (95% CI, .40 to .70) and .23 (95% CI, .07 to .44) for acute and chronic GVHD, respectively. In summary, albeit limited by numbers of available studies, pooled analyses of prospective studies demonstrate encouraging responses after ECP treatment in acute and chronic GVHD after failing corticosteroids. Further research efforts are needed to improve organ-specific responses.

According to the threshold model, when faced with a decision under diagnostic uncertainty, physicians should administer treatment if the probability of disease is above a specified threshold and withhold treatment otherwise. The objectives of the present study are to a) evaluate if physicians act according to a threshold model, b) examine which of the existing threshold models [expected utility theory model (EUT), regret-based threshold model, or dual-processing theory] explains the physicians’ decision-making best.