Endoscopic Ablation Therapy for Barrett's Oesophagus. A Clinicopathologic Study on Efficacy
Since Barrett’s oesophagus is a major risk factor for developing oesophageal adenocarcinoma, most centres have implemented endosocopic biopsy surveillance programs to detect precursor stages of adenocarcinoma (i.e. low grade dysplasia (LGD) and high grade dysplasia (HGD)). There is much interest in non-invasive, low-risk, ablative techniques that can eliminate precursor stages or early invasive cancer, since oesophagectomy, mostly performed once HGD or invasive cancer has developed, confers a high mortality and morbidity. The most commonly used techniques are thermal destruction by argon plasma coagulation (APC) and photochemical destruction by photodynamic therapy (PDT). Photochemical ablation using PDT is based on an intracellular accumulation of the photosensitizer protoporphyrin IX (PpIX) in tissue. There are different photosensitizers. The most common used are an enriched form of hematoporphyrin (Photophrin) and 5-aminolevulinic acid (ALA). ALA is a precursor molecule in the heme biosynthetic pathway that induces an endogenous production of PpIX. Photophrin is given to patients intravenously, whereas ALA is administered orally. PpIX is activated by photo-irradiation using laser light with an appropriate wavelength. This generates singlet oxygen production resulting in tissue destruction. APC employs a cautery probe that transfers electrical energy through ionized, electro conductive plasma of argon gas to the tissue surface, again resulting in tissue destruction.
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