How is extracorporeal photopheresis (ECP) performed?

Updated: Nov 21, 2016
  • Author: Vikas Shrivastava, MD; Chief Editor: William D James, MD  Dirk M Elston, MD  more...
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Answer

Answer

Extracorporeal photopheresis (ECP) involves the collection of white blood cells with subsequent exposure to a photosensitizer, 8-methoxypsoralen (8-MOP), and ultraviolet A (UVA) radiation. UVA activates 8-MOP and causes crosslinkage of DNA. [6, 7]

ECP is performed via intravenous access and has 3 stages: (1) leukapheresis, (2) photoactivation, and (3) reinfusion of treated cell product back to the patient.

A number of open and closed systems exist. In the United States, only closed systems have been FDA approved. Closed systems integrate drug photoactivation and reinfusion, thus lowering risk of infection, contamination, and errors during reinfusion. [1]

Therakos (Westchester, Pa.) has developed several generations of closed systems. Their CELLEX Photophoresis System is a third-generation system that uses a continuous-flow centrifuge. [5] Compared with the second-generation UVAR XTS system, it requires a lower volume of blood and less time to complete. [8] Depending on which generation of system is used, the process can take between 1.5 and 4 hours to complete.

The procedure for the widely used UVAR XTS system is outlined below:

  • Peripheral intravenous or central venous access is established in the patient. The newer CELLEX system can take advantage of double-needle access. [5]

  • Blood is passed through multiple cycles of leukapheresis. The volume of blood and number of cycles depends on the patient’s hematocrit and body weight (kg). [6] At the end of each leukapheresis cycle, the red blood cells and plasma are returned to the patient. Only a small percentage (5-10%) of the patient’s WBCs are extracted and treated. [6]

  • The collected WBCs are mixed with heparin, saline, and 8-MOP, which intercalates into the DNA of the lymphocytes and makes the cells more susceptible to apoptosis when exposed to UVA radiation. Of note, older procedures involved the use of oral 8-MOP which resulted in greater GI toxicity and unpredictable drug levels. [6, 7]

  • The mixture is passed through a sterile cassette surrounded by UVA bulbs, resulting in an average UVA exposure of 1.5-2 J/cm2 per lymphocyte. [6, 7]

  • The treated WBC mixture is returned to the patient.

  • For cutaneous T-cell leukemia (CTCL), this procedure is usually conducted on 2 consecutive days every 2-4 weeks for 6 months, although a variety of treatment intervals, treatment durations, and tapering schedules exist for different indications. Accelerated regimens are typically used in graft versus host disease (GVHD). [6]


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