Pleural mesothelioma is an aggressive cancer that attacks the membrane surrounding the lungs. Photodynamic therapy (PDT), which uses light and a photosensitizing drug, can be used to kill residual cancer cells after debulking surgery. Uniform distribution of the light is key to the effectiveness of this mesothelioma therapy.
Now, a report presented at the 58th Annual Meeting of the American Association of Physicists in Medicine suggests that the process can be even more effective if an infrared camera is used to track the motion of the light source during treatment, ensuring even distribution.
Photodynamic Therapy for Mesothelioma
Photodynamic therapy for malignant mesothelioma is an emerging treatment that is primarily available only in larger centers. It is typically used in conjunction with lung-sparing pleurectomy/decortication surgery, during which the surgeon tries to remove as much of the pleural mesothelioma tumor as possible, along with other at-risk tissues.
The patient receives a dose of the photosensitizing drug a day prior to surgery. Cancer cells hold on to the photosensitizing drug longer than healthy cells, allowing for a highly targeted treatment approach.
After mesothelioma surgery, the surgeon directs a powerful cancer-killing laser light on the end of an endoscope into the thoracic cavity with the goal of destroyed any remaining cancer cells that may have been left behind.
Because PDT works differently than chemotherapy, radiation or surgery, it can be used along with these therapies as part of a multi-modality approach to mesothelioma treatment.
Tracking Cancer-Killing Light
According to Biophysicist Michele Kim and her colleagues at the University of Pennsylvania, PDT for mesothelioma is typically monitored by isotopic light detectors placed at specific locations inside the pleural cavity.
But a “real-time” tracking system that incorporates infrared camera technology may allow the user to be more precise with the light delivery, potentially making the treatment more effective and improving mesothelioma survival.
“It is possible to use the feedback system to deliver a more uniform dose of light throughout the pleural cavity,” reports Kim and her colleagues. “In a phantom study, the light distribution was improved by using real-time guidance compared to the distribution when using detectors without guidance.”
Ongoing PDT Mesothelioma Research
Penn’s previous studies on photodynamic therapy in combination with lung-sparing surgery have produced some of the best mesothelioma survival results to date.
A 2013 Penn study published in the Annals of Cardiothoracic Surgery showed a median survival of 31.7 months among 38 mesothelioma patients who underwent surgery and PDT. The results were especially notable since all of the patients had advanced disease. Patients in the study with the epithelioid type of mesothelioma survived even longer.
University of Pennsylvania researchers are in the midst of an NIH-funded clinical trial of PDT in pleural mesothelioma that began in 2014.
Kim, M, et al, “Update on a Real-Time Treatment Guidance System Using an IR Navigation System for Pleural PDT”, December 2016, Medical Physics, pp. 3672