Does Offline Beat Inline Treatment: Investigation into Extracorporeal Photopheresis

Extracorporeal photopheresis is a therapy based on the induction of apoptosis to cells harvested from peripheral blood, followed by direct retransfusion. Currently, there are two approaches: inline procedures, where cell harvesting, 8-methoxypsoralen (8-MOP) incubation, and UV irradiation is performed with a single device, and offline procedures, with collection in one device, followed by 8-MOP incubation/UV irradiation using a second device.

In a prospective crossover study, we compared an inline (Cellex, Therakos) with an established offline procedure (Optia, Terumo, and MacoGenic G2, Macopharma) in 6 patients, focusing on cell composition and apoptosis induction after 24 h. In total, 32 photopheresis treatments per device were performed.

We observed an overall 2-fold higher number of apoptotic "target" cells for each patient with offline treatment. All yields were stratified per patient. Yields were compared as ratio offline/inline for CD3+ (2.5-fold), CD4+ (2-fold), CD8+ (2.8-fold), CD56+ (2.8-fold), CD19+ (1.8-fold), CD15+ (0.5-fold), and CD14+ (2.2-fold) cells. Apoptosis induction was measured after 24 h with Annexin V/7-AAD for early and late apoptosis rates of CD3+ (CD4+, CD8+) and CD56+ cells. CD3+ cells of the inline treatment had an average of 88% (26% early, 62% late) of apoptotic cells compared to 75% (34% early, 41% late) in the offline treatment. Procedure duration ranged from 80 to 100 min inline, with a maximum of 1,500 mL processed blood, and 125-140 min offline, with at least 3,000 mL processed blood, depending on blood flow. Average hematocrit levels of the products were 2.7% inline versus 1.7% offline.

The offline procedure, as established in our department, provides more apoptotic cells for treatment. The increased number of mononuclear cells collected outweighs a slightly reduced apoptosis rate after 24 h in comparison to the inline procedure. Besides this, the final decision for one or the other procedure has to take into account additional aspects, such as peripheral white blood cell count, hematocrit, and weight of the patient, required before apheresis, extracorporeal volume, and, last but not least, overall costs. The final criterion, however, has to be the reported clinical efficacy of the system applied.