In vivo determination of tumor optical parameters in esophageal carcinoma

Background and Objective: Dose dependence of light cannot be discussed on t he basis of dose alone. On a more fundamental scientific level, the propaga tion of light in tissue depends on optical parameters of treated tumor tiss ue. In a prospective, nonrandomized study, in vivo optical parameters of es ophageal carcinoma were studied. Study Design/Materials and Methods: Nineteen intraoperative measurements of tumor optical parameters in six patients with esophageal carcinoma were pe rformed. After diagnostic work-up and clinical staging, right-sided, poster olateral thoracotomy, and dissection of the esophagus were carried out. The tumor site was exposed and continuous endoluminal irradiation was started during determination of light penetration at the level of the adventitia of the esophagus. The tumors were located exactly between the endoluminal irr adiation source and measurement probe in the thoracic cavity. Measurements were performed on tumors having different diameters to show the relationshi p between tumor diameter, extinction coefficient, and light penetration dep th. Results: The endoluminal incident intensity was 18.5 mW/cm(2). At a tumor d iameter of 4, 6, 8, and 9 mm measured intensity of 5.12, 2.28, 0.88 and 0.6 5 mW/cm(2), an extinction coefficient of 0.321, 0.349, 0.381, and 0.373, as well as penetration depth of 3.21, 2.87, 2.62, and 2.68 mm, respectively, could be measured. The correlation of tumor optical parameters, tumor diame ter, penetration depth, and treatment time were ex pressed by the relative correction factor for different tumor diameters. Conclusion: The knowledge of tumor optical properties seems to be necessary to adapt dosimetry to the individual situation and manage optimal results of PDT in esophageal cancer. (C) 2000 Wiley-Liss, Inc.