Improvement in Photodynamic Therapy for Malignant Pleural Mesothelioma

Improvement in Photodynamic Therapy for Malignant Pleural Mesothelioma

An improved lighting and tracking technique in photodynamic therapy (PDT) for treating malignant pleural mesothelioma (MPM) was successful in the laboratory using a mock-up of a human hemithorax.

The study, “Real-time light dosimetry for intra-cavity photodynamic therapy: Application for pleural mesothelioma treatment,” has been accepted for publication in the journal Photodiagnosis and Photodynamic Therapy.

MPM is an aggressive cancer in the thin layer of tissue surrounding the lungs known as the pleura. Its most common cause is inhalation of asbestos fibers. Treatment of MPM now relies on surgery, combined with chemotherapy and radiotherapy.

“Surgery offers the best chance of survival for this still incurable disease, however after the most complete tumor resection, microscopic tumor cells persist and surgery should be associated with an adjuvant local treatment. PDT appeared as a potential option for an effective intra-operative complement to surgery,” wrote Nacim Betrouni, PhD, and his colleagues from the Institut National de la Santé et de la Recherche Médicale (INSERM).

PDT is a new technique used to kill tumor cells with photosensitizer (PS) drugs (drugs that are activated by light), a light source to activate the PS drugs, and oxygen, which is needed in the chemical reaction that causes tumor cell death.

In PDT, a light source is moved around (in the pleural cavity in the case of MPM), to activate the PS drugs that kill off tumor cells left after the tumors are removed with surgery.

The trick is to guide and monitor the light source properly to ensure complete treatment, and this means that the location and intensity of the light from the light source has to be tracked during the procedure.

This research makes PDT for MPM easier to use, and more thorough treatment possible, by using an applicator for the light source that provides the light and measures the light delivered, at the same time. The researchers also track the light applicator’s movement in real time so the surgeon can see a display showing location and light intensity based on a color scheme.

They tested the new system successfully using a human-sized hemithorax (one side of the chest) made of plaster.

“In this study we propose a novel approach based on the combination of light distribution modeling with spatial localization of the light applicator for real time estimation and display of the applied dose on medical images,” the researchers wrote. “The feasibility approach is demonstrated for intrapleural PDT of malignant pleural mesothelioma.”

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