Light Fluence Rate and Tissue Oxygenation (StO2) Distributions Within the Thoracic Cavity of Patients Receiving Intraoperative Photodynamic Therapy for Malignant Pleural Mesothelioma

• Published in: Photochemistry and photobiology Vol. 96; no. 2; pp. 417 - 425
• Main Authors: Dupre, Pamela J., Ong, Yi Hong, Friedberg, Joseph, Singhal, Sunil, Carter, Shirron, Simone, Charles B., Finlay, Jarod C., Zhu, Timothy C., Cengel, Keith A., Busch, Theresa M.
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.03.2020
• Subjects: Depletion; Exposure; Female; Fluence; Humans; Intraoperative Period; Light; Light therapy; Male; Mediastinum; Mesothelioma; Mesothelioma, Malignant - drug therapy; Mesothelioma, Malignant - metabolism; Mesothelioma, Malignant - surgery; Oxygen; Oxygen - metabolism; Oxygen depletion; Oxygenation; Photochemotherapy; Photodynamic therapy; Pleural Neoplasms - drug therapy; Pleural Neoplasms - metabolism; Pleural Neoplasms - surgery; Thoracic Cavity - pathology; Thorax; Tissues
• ISSN: 0031-8655; 1751-1097; 1751-1097
• DOI: 10.1111/php.13224

The distributions of light and tissue oxygenation (StO2) within the chest cavity were determined for 15 subjects undergoing macroscopic complete resection followed by intraoperative photodynamic therapy (PDT) as part of a clinical trial for the treatment of malignant pleural mesothelioma (MPM). Over the course of light delivery, detectors at each of eight different sites recorded exposure to variable fluence rate. Nevertheless, the treatment‐averaged fluence rate was similar among sites, ranging from a median of 40–61 mW cm−2 during periods of light exposure to a detector. StO2 at each tissue site varied by subject, but posterior mediastinum and posterior sulcus were the most consistently well oxygenated (median StO2 >90%; interquartile ranges ~85–95%). PDT effect on StO2 was characterized as the StO2 ratio (post‐PDT StO2/pre‐PDT StO2). High StO2 pre‐PDT was significantly associated with oxygen depletion (StO2 ratio < 1), although the extent of oxygen depletion was mild (median StO2 ratio of 0.8). Overall, PDT of the thoracic cavity resulted in moderate treatment‐averaged fluence rate that was consistent among treated tissue sites, despite instantaneous exposure to high fluence rate. Mild oxygen depletion after PDT was experienced at tissue sites with high pre‐PDT StO2, which may suggest the presence of a treatment effect. During intraoperative photodynamic therapy (PDT) for malignant pleural mesothelioma, illumination is delivered to the thoracic cavity (A), resulting in treatment‐averaged light exposures of ~40–60 mW cm−2 for most tissues of the chest (B). Tissue hemoglobin oxygen saturation (StO2) is measured before and after PDT, revealing that tissues with better oxygenation before PDT are more likely to experience a decrease in oxygenation shortly after PDT (ratio < 1), suggesting the presence of a treatment‐induced effect (C). Tissues sites are the apex, anterior chest wall (ACW), posterior chest wall (PCW), posterior mediastinum (PM), diaphragm (Diaph), pericardium (Peri), posterior sulcus (PS), and anterior sulcus (AS).