Abstract No. 347 Safety and Feasibility of Photodynamic Therapy as an Adjunct to Percutaneous Drainage of Deep Tissue Abscesses: Phase 1 Clinical Trial Results

Photodynamic therapy (PDT) is a technique that relies on the combination of a light-sensitive drug (photosensitizer), visible light excitation, and molecular oxygen to generate cytotoxic reactive oxygen. This technique has been successfully used to treat superficial infections and cancer. Deep tissue abscesses (DTA) are a common pathology treated by the interventional radiology department. As antibiotic resistance is on the rise and not all abscesses are responsive to the standard of care, new options for treatment in addition to the standard percutaneous drainage and antibiotics are needed. In this first of its kind study the safety and feasibility of PDT for sterilization of DTA was studied. This phase I clinical trial (ClinicalTrials.gov Identifier: NCT02240498) employed a dose escalation scheme with a 3+3 dose escalation design modulating the laser exposure time. All subjects first received standard of care image-guided percutaneous drainage. Following drainage, sterile methylene blue was infused into the abscess cavity at a concentration of 1 mg/mL and left to incubate for 10 minutes. The cavity with then filled with a sterile 1% lipid emulsion solution to homogenize the light distribution at the abscess wall. A sterile optical fiber was then advanced through the catheter, in order to deliver treatment light at 665 nm. Light was then delivered for 5-30 minutes. We successfully treated 18 subjects with methylene blue PDT at the time of percutaneous abscess drainage. No study-related adverse or serious adverse events were encountered; the procedure was well-tolerated by all subjects. Preliminary analysis suggests that the resolution of clinical symptoms was more rapid in those receiving longer durations of light delivery (p=0.03) and that catheter drainage volume was decreased at longer light delivery durations although this difference was not significant (p=0.37). Deep tissue abscess cavity sterilization via methylene blue PDT is a safe and feasible treatment, with preliminary evidence for improvement in clinical response.