Photodynamic therapy for Barrett’s esophagus: does light still have a role?

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Abstract
Photodynamic therapy consists of three elements [ 2 ]. There is a drug, which can be administered either orally or intravenously, that is supposed to be preferentially taken up within the Barrett’s mucosa. The most commonly used oral drug, 5-aminolevulinic acid (ALA), generally is administered within 4 hours of photoradiation, while the intravenous drug sodium porfimer must be given 48 hours before photoradiation. The oral medication certainly would make therapy simpler but is not used in the United States except as a topical application. Once adequate concentrations of the drug are achieved, photoradiation can be applied. This generally uses “red” wavelengths (630 – 635 nm) of light, which activate the drug. The drug interacts with molecular oxygen, causing it to form a singlet oxygen state, which then can interact with the tissue, causing cell death ([ Fig. 1 ]). Fig. 1 Photodynamic therapy in its current iteration. Light is used to activate a drug in the tissue. The drug absorbs the light energy and interacts with oxygen causing singlet oxygen which mediates cell death. Although this sounds complicated, this is one of the simplest methods by which phototherapy can be delivered. Technically, it is a very easy procedure to perform which ensures that treatment can be performed without much variation in response due to variation in endoscopic skills. The administration of light can be done through very small fibers that can fit through any endoscope or even potentially come from nonendoscopic light sources. In addition, the photoradiation periods are relatively short and do not require much endoscope motion, which makes the therapy easily tolerated by most patients. The simplicity of this treatment would indicate that it has the highest chance of being effectively introduced into community practice. A great deal of the ablative therapies currently available are fairly complex and are suitable only for tertiary referral centers where the expertise exists to utilize these therapies. This situation is analogous to esophagectomy where, if it is performed in expert centers, mortality rates are often less than 3 %, even in the older population of patients who are prone to Barrett’s esophagus [ 3 ]. If one examines, though, the mortality rate in the community, they can easily approach 18 % in centers where esophagectomy is not often performed. The same issues will most likely apply to complicate complex endoscopic procedures. In fact, this type of cancer therapy is probably more translatable to practice, not only in this country, but also in countries with limited healthcare resources where more complex modalities are difficult to deliver.