Tuesday, June 28, 2011

Light-Based Therapy Helps Some Pleural Mesothelioma Patients Live Longer; Researchers Call Results ‘Encouraging’

Breakthrough medical treatments often occur when researchers are focused on solving a different problem. It’s the circuitous path of scientific discovery.

In a study published in the June issue of Annals of Thoracic Surgery, researchers at the University of Pennsylvania report on a novel treatment technique that holds the promise of significantly extending the lives of pleural mesothelioma patients.

Malignant pleural mesothelioma is an aggressive cancer of the lining of the lung caused by inhaling asbestos. Asbestos exposure typically occurs 20 to 50 years before the patient develops symptoms of the aggressive respiratory cancer. But once mesothelioma appears, patients typically die within 9 to 12 months.

In the new study, pleural mesothelioma patients who underwent lung-sparing surgery in combination with an experimental light-based cancer treatment called photodynamic therapy, have shown unusually long overall survival, the University of Pennsylvania researchers reported. Most of the patients were older and had advanced stage III and IV cancer.

“The findings from our study are particularly notable because many of the patients in this study would often be excluded from surgery-based therapy because of their advanced age or unfavorable (cancer) characteristics,” said Dr. Joseph Freidberg, MD, a thoracic surgeon and co-director of the Penn Mesothelioma and Pleural Program in a press release.

Dr. Freidberg said the patients who underwent lung sparing surgery combined with photodynamic therapy (PDT) from 2004 to 2008 have experienced unusually long overall survival rates.

Photodynamic therapy is an emerging cancer treatment that that uses a drug called a photosensitizer and a specific type of light to kill cancer cells. The light therapy penetrates the tissue to a depth of several millimeters.

“We were completely caught off guard when the analysis revealed a significantly longer survival for patients who retained two lungs,” Friedberg said.

While the size of the study was a limitation, Freidberg called the results encouraging. They certainly offer some hope for mesothelioma patients and their families.

The Penn researchers compared the survival of two groups of mesothelioma patients who underwent different treatments. One group of 14 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.

The other group of 14 mesothelioma patients underwent a radical pleurectomy, in which the diseased lining of the lung is removed, but the patient’s lung itself is spared.

The two groups totaling 19 men and 9 women overall had similar demographics, and both groups received photodynamic therapy during surgery.

The median survival for the patients who underwent the extrapleural pneumonectomy combined with the light therapy was about 8.4 months. Meanwhile, enough of the mesothelioma patients in the second group remained alive at the end of two years that the rearchers have yet to be able to calculate their median survival.

“Why this is happening is unclear and has emerged as the focus of our continuing research,” Friedberg said. “The possibility exists that residual PDT-treated microscopic disease induced a vaccine effect or potentially enhanced the effect of adjuvant treatments.”

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

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

Approximately 3,000 people are diagnosed with mesothelioma in the United States each year. Most are workers and veterans who were exposed to asbestos decades ago, and the families of asbestos workers.