A New Light Delivery System for Photodynamic Therapy with Aminolevulinic Acid (ALA) for Treatment of High-Grade Dysplasia in Barrett's Esophagus

Abstract

Past light delivery systems for photodynamic therapy (PDT) for the treatment of high-grade dysplasia (HGD) in Barrett's esophagus (BE) have depended on centering balloons designed to maintain cylindrical diffuser fibers in the mid-esophageal lumen for even light distribution. A disadvantage of this system is that placement largely depends on prior endoscopic measurements while the balloon is only seen from the top. Aim: Describe our experience with a new light delivery system utilizing a transparent plastic sheath fitting over the endoscope, allowing direct observation of fiber placement in the treatment area. Methods: PDT Sheath (DUSA) is a single-use, inflatable, non-distensible, thin-walled tube with an 18 mm diameter distal balloon. Distal window, balloon, and sheath are transparent to allow direct visualization of the treatment area. Cylindrical diffusing fibers of varying lengths are passed through the biopsy channel of the endoscope, which is withdrawn an appropriate distance from the distal window to allow full extension of the fiber with endoscopic control. The sheath is designed to fit over a standard 9.8 mm endoscope. A locking mechanism restricts movement of the sheath independent of the scope. Air-seals on the ports maintain inflation and deflation using a pump with a toggle switch. A suction tube is built into the sheath to remove fluids that might pool above the inflated balloon. After multiple ex-vivo sessions with the DUSA PDT Sheath, a mock PDT treatment was successfully performed on an anesthetized pig. We then treated our first 3 patients (extensive BE with HGD, lengths 8, 8, 4 cm) with the sheath 4-6 hours after the administration of ALA (60 mg/kg) with a light dose of 150 J/cm2 at 635 nm wavelength provided by a diode laser. Results: Slight technical difficulty in moving the endoscope within the sheath was overcome using silicon lubricant on the outside of the endoscope. We had no difficulty passing the endoscope sheath assembly into the esophagus, and were able to see through the distal balloon for accurate placement of the scope and fiber. All patients had marked PDT mucosal ablation of BE, and 2 of 3 had elimination of HGD at 1 month follow-up. Conclusion: PDT sheath appears to be a safe and effective device for ALA-PDT in our initial experience. Further tests are planned to optimize light dose using this new device. Supported by a grant from DUSA, Inc. Past light delivery systems for photodynamic therapy (PDT) for the treatment of high-grade dysplasia (HGD) in Barrett's esophagus (BE) have depended on centering balloons designed to maintain cylindrical diffuser fibers in the mid-esophageal lumen for even light distribution. A disadvantage of this system is that placement largely depends on prior endoscopic measurements while the balloon is only seen from the top. Aim: Describe our experience with a new light delivery system utilizing a transparent plastic sheath fitting over the endoscope, allowing direct observation of fiber placement in the treatment area. Methods: PDT Sheath (DUSA) is a single-use, inflatable, non-distensible, thin-walled tube with an 18 mm diameter distal balloon. Distal window, balloon, and sheath are transparent to allow direct visualization of the treatment area. Cylindrical diffusing fibers of varying lengths are passed through the biopsy channel of the endoscope, which is withdrawn an appropriate distance from the distal window to allow full extension of the fiber with endoscopic control. The sheath is designed to fit over a standard 9.8 mm endoscope. A locking mechanism restricts movement of the sheath independent of the scope. Air-seals on the ports maintain inflation and deflation using a pump with a toggle switch. A suction tube is built into the sheath to remove fluids that might pool above the inflated balloon. After multiple ex-vivo sessions with the DUSA PDT Sheath, a mock PDT treatment was successfully performed on an anesthetized pig. We then treated our first 3 patients (extensive BE with HGD, lengths 8, 8, 4 cm) with the sheath 4-6 hours after the administration of ALA (60 mg/kg) with a light dose of 150 J/cm2 at 635 nm wavelength provided by a diode laser. Results: Slight technical difficulty in moving the endoscope within the sheath was overcome using silicon lubricant on the outside of the endoscope. We had no difficulty passing the endoscope sheath assembly into the esophagus, and were able to see through the distal balloon for accurate placement of the scope and fiber. All patients had marked PDT mucosal ablation of BE, and 2 of 3 had elimination of HGD at 1 month follow-up. Conclusion: PDT sheath appears to be a safe and effective device for ALA-PDT in our initial experience. Further tests are planned to optimize light dose using this new device. Supported by a grant from DUSA, Inc.