A Phase 2 Study of Methylene Blue Photodynamic Therapy for Treatment of Breast Abscesses

All subjects will receive ultrasound-guided percutaneous abscess drainage in a procedure room. The site will be prepared and dressed following standard of care sterile procedure, and a needle/catheter will be advanced under ultrasound guidance into the abscess. The abscess will be drained by syringe aspiration, and the cavity will be flushed with sterile saline. Aspirated abscess fluid will be delivered to the Clinical Microbiology Laboratory for processing, including bacterial identification and antibiotic susceptibility testing.

Following standard of care breast abscess drainage, for subjects randomized to the photodynamic therapy arm, sterile, clinical-grade methylene blue will be infused into the abscess cavity at a concentration of 100 µg/mL via the same needle/catheter used for drainage. The volume introduced will be matched to the amount of abscess material aspirated during the standard of care drainage. After a 10-minute incubation interval, methylene blue will be aspirated and the cavity flushed with sterile saline to remove methylene blue that has not been taken up by microbes.

For subjects randomized to the photodynamic therapy arm, immediately prior to illumination a lipid emulsion will be administered directly to the abscess through the drainage needle/catheter at a concentration of 0.1%. This lipid emulsion will be either Intralipid or Nutrilipid. The lipid emulsion serves to gently distend the cavity, and through light scattering, homogenize the light dose to the walls of the cavity. The volume administered will be matched to the amount of abscess material aspirated during the standard of care drainage. Following laser illumination, the lipid emulsion will be aspirated and the cavity flushed with sterile saline.

For subjects randomized to the photodynamic therapy arm, a sterile, single-use optical fiber will be advanced to the approximate center of the abscess cavity via the same needle/catheter used for abscess drainage under ultrasound guidance. This will be connected to the clinical laser system via SMA connector for delivery of treatment light.

For subjects randomized to the photodynamic therapy arm, laser illumination for photodynamic therapy will be delivered by a laser system operating at 665 nm (ML7710, Modulight, Tampere, Finland) at a fluence rate of 20 mW/cm\^2. The laser power required to achieve this fluence rate will be calculated based on abscess size. Illumination will be delivered for \~20 minutes, resulting in a total delivered fluence of 25 J/cm\^2.

For subjects randomized to the photodynamic therapy arm, the photodynamic therapy procedure comprises the methylene blue, lipid emulsion, insertion of optical fiber, and laser illumination interventions.