Light Fluence Rate and Tissue Oxygenation (S_tO₂) Distributions Within the Thoracic Cavity of Patients Receiving Intraoperative Photodynamic Therapy for Malignant Pleural Mesothelioma

Abstract

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.

Perspectives on interstitial photodynamic therapy for malignant tumors

“…[98][99][100] Furthermore, many dosimetry methods have already been investigated and integrated into the treatment platform. These dosimetry methods have included measuring photofrin photobleaching, 100 ROS production, 98 and light fluence, to name a few. 99,101 For this indication, IPDT could play a further role in treatment and possibly expand the number of treatment sessions or lengthening the treatment out beyond just using IPDT as an adjunct treatment postsurgery.…”

“… 97 PDT has been used previously with success in small clinical trials. 98 – 100 Furthermore, many dosimetry methods have already been investigated and integrated into the treatment platform. These dosimetry methods have included measuring photofrin photobleaching, 100 ROS production, 98 and light fluence, to name a few.…”

Editorial: Dosimetry Study in Photodynamic Therapy for Diagnosis, Precision Treatment and Treatment Evaluation

“…Creative direct and (mostly) indirect measurements have been developed to navigate the treatment process [7][8][9]. Among current methods, it can merely measure the fluorescence intensity [10,11] or might require the comprehensive measurement of many relevant parameters in the surgical procedure of clinical studies [12]. In practice, most clinical PDT procedures around the world only involve the calculation of drug dose and delivered light dose at the lesion surface.…”

First in human measurements of abscess cavity optical properties and methylene blue uptake prior to photodynamic therapy byin vivodiffuse reflectance spectroscopy

“…Lietke et al used a similar approach in designing treatment plans for malignant glioma recurrences 13 . In the context of a larger body space, Dupre et al reported on the performance of surface contact spatially-resolved diffuse reflectance spectroscopy prior to PDT of the pleural cavity 14 . These measurements, along with real-time fluence monitoring 15 , were used to deliver uniform light doses to highly heterogeneous subjects.…”