A new long-range through-the-scope balloon applicator for photodynamic therapy in the esophagus and cardia

Background and Study Aims: Photodynamic therapy (PDT) is a new local, endos copically controlled therapeutic technique based on the sensitization of ma lignant and precancerous lesions prior to light-induced tissue destruction. PDT of Barrett's esophagus with severe dysplasia, or of mucosal carcinomas and superficial squamous-cell cancer of the esophagus, requires light appl ication devices allowing homogeneous illumination of the tissue surface in spite of esophageal motility and respiratory movement. On the basis of a co mmercially available through-the-scope balloon system, we developed a long- range light applicator for homogeneous and circumferential irradiation duri ng PDT, and describe here the initial clinical experience with the device. Patients and Methods: The new balloon applicator consists of a flexible cyl indrical diffuser fiber with a length of up to 10 cm, depending on the lesi on to be illuminated, and an inflatable balloon based on the type of balloo n used for esophageal dilation. The balloon is made of a transparent polyur ethane membrane with negligible absorption (<5%) at lambda = 600-700 nm, an d it can be positioned through the biopsy channel of a conventional endosco pe, with direct endoscopic visualization of the targeted lesion. The light intensity distribution perpendicular to the optical axes of the diffuser wa s measured for red laser light (lambda = 632.8 nm) and for green laser ligh t (lambda = 542 nm). The study of photodynamic treatment included two women and four men (aged 4 8-79 years) with histologically proved high-grade dysplasia (n = 2) or muco sal cancer in Barrett's esophagus (n = 2) and superficial squamous-cell can cer (SCC) (n = 2), who had undergone EUS staging showing uT0 or uT1N0. Lase r light irradiation was conducted after oral ingestion of 5-amino-levulinic acid (5-ALA) or intravenous administration of meta-(tetrahydroxyphenyl)chl orin (mTHPC). Results: Both in vitro and in vivo, precise positioning of the new applicat ion system at the targeted tissue and homogeneous illumination were feasibl e, safe and effective. The total efficiency of transmitted light at wavelen gths of lambda = 632.8 nm and lambda = 542 nm was 85-90 %. A high degree of homogeneity: was measured with applicator lengths of between 15 mm and 95 mm, and the maximum deviation from the mean intensity extended over a range of 40 % over the total length of 80 mm. High-grade dysplasia was eradicate d in all patients, and in addition mucosal cancer was successfully destroye d in three-quarters of them, requiring an average of 1.3 treatment sessions , with a mean follow-up of 12 months (range 10-15 months). Conclusions: This centering balloon system may in the future be capable of improving light application techniques during esophageal photodynamic thera py, making PDT a more reliable alternative modality for minimally invasive treatment of high-grade dysplasia and early Barrett's esophagus or squamous -cell carcinoma, as compared with esophagectomy.