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Photodynamic Therapy Offers Hope For Extending Lives Of Mesothelioma Patients

An experimental light therapy treatment studied by medical researchers at the University of Pennsylvania offers promise for significantly prolonging the lives of pleural mesothelioma patients.

In a 2011 study published in the Annals of Thoracic Surgery, pleural mesothelioma patients who underwent lung-sparing surgery, in combination with a light-based cancer treatment called photodynamic therapy, have shown unusually long overall survival, the researchers reported.

Malignant pleural mesothelioma is an aggressive cancer of the lining of the lung associated with inhaling asbestos. Asbestos exposure typically occurs 20 to 50 years before symptoms of pleural mesothelioma appear. Once the aggressive cancer develops, patients typically die within nine to 12 months.

How Photodynamic Therapy Works

Photodynamic therapy is an emerging cancer treatment that entails the use of photosensitizing drugs injected into cancerous tissue, followed by penetrating beams of light that kill cancer cells. Besides killing cells directly, photodynamic therapy can initiate an immune response against cancer. The use of photodynamic therapy for mesothelioma patients is still experimental.

The Penn researchers compared the survival of two groups of pleural mesothelioma patients who underwent different surgical treatments combined with photodynamic therapy and chemotherapy from 2004 to 2008. The strategy of any multi-pronged cancer treatment regimen is to use surgery to remove cancerous tumors as completely as possible, and then use other therapies to control any remaining cancer cells.

Mesothelioma Patients

One group of 14 mesothelioma patients underwent a modified version of radical surgery to remove a lung and the lining of the lung, a procedure known as an extrapleural pneumonectomy. The radical surgery was combined with the light-based cancer therapy while each patient was in the operating room. The second group of 14 mesothelioma patients underwent a pleurectomy, in which the diseased lining of the lung was removed, but the patient’s lung itself was spared.

The two groups, with 19 men and 9 women, had similar demographics, and both groups received the photodynamic therapy. The patients ranged in age from 27 years old to 81 years old. Most patients also received pemetrexed-based chemotherapy, and some underwent radiation.

The initial aim of the research was to determine if using light therapy would allow less extensive surgery to be used. The second aim, based on previous research at Penn, was to determine if photodynamic therapy would improve survival. Penn is one of only two medical centers that use photodynamic therapy to treat pleural mesothelioma.

Research Findings

There was a significant difference in the overall survival of the two groups of patients, the researchers reported.

The median survival for the patients who underwent the extrapleural pneumonectomy to remove a lung combined with the light therapy was about 8.4 months.

But enough of the mesothelioma patients in the second group who underwent lung-sparing surgery remained alive after two years that the researchers have yet to be able to calculate their median survival. That contrasts with the typical survival of nine months to 13 months for mesothelioma patients who undergo pleurectomy based on other studies.

The findings are particularly notable because most of the patients in the study had advanced stage III and IV cancer. They would not otherwise have been good candidates for radical surgery because of their age or cancer characteristics.

Photodynamic Therapy: A New Option?

Given the results, the researchers say that removal of the cancerous lining of the lung (a radical pleurectomy) combined with photodynamic therapy is a reasonable option for appropriate pleural mesothelioma patients. A growing body of evidence supports photodynamic therapy as an effective way to induce an immune system response against cancer. The researchers say the procedure can serve as the backbone of multi-pronged surgery-based treatments for mesothelioma.

A larger study investigating the effectiveness of this treatment approach is currently under way at Penn.

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