Pleural mesothelioma, a malignancy of the lung lining caused by breathing asbestos, is notoriously difficult to treat. While they can improve quality of life, traditional cancer therapies, including chemotherapy, radiation and surgical intervention have not been shown to improve survival rates in most mesothelioma patients beyond a few months.
Researchers around the world are experimenting with advanced treatment options that may give mesothelioma patients new hope. A new study on Intensity Modulated Radiation Therapy (IMRT) as part of a multi-modality treatment protocol appears to show improved safety over earlier studies that incorporated the same technology.
IMRT is an advanced method of radiotherapy that uses a linear accelerator to deliver precise high doses of radiation directly into a tumor. One of the risks of such high dose radiation in the lung is the development of pneumonitis, a potentially fatal inflammation of the lung tissue. A 2006 Brigham and Women’s Hospital analysis of 13 mesothelioma patients treated with IMRT, surgery, and chemotherapy found that six of the patients developed fatal cases of pneumonitis. A year later, the same group of researchers found that a greater percentage of healthy lung tissue could be spared, and the risk of complications reduced, by narrowing the IMRT radiation field.
Now, a group of University of Pennsylvania researchers has demonstrated promising results by pairing a narrowed IMRT field with other therapies to destroy mesothelioma cells in the lung lining. The researchers treated 11 malignant pleural mesothelioma patients with a combination of IMRT, extrapleural pneumonectomy (a surgical procedure), and intraoperative photodynamic therapy (using light to kill cancer cells). The IMRT was administered post surgically in all 11 patients.
Writing in the September issue of the journal Cancer Biology & Therapy, the researchers report that only one of the mesothelioma study subjects experienced respiratory failure as a side effect of the radiation, but did not need to be put on a ventilator. The researchers say “Multimodality therapy combining surgery with increased doses of radiation using IMRT and newer treatment modalities such as PDT, appears safe.”
They say that more analysis will be needed to confirm the efficacy of this approach and to determine its effect on survival in pleural mesothelioma patients. In addition, the University of Pennsylvania team says further refinements need to be made to IMRT techniques to further reduce toxicity and improve dose delivery. Such improvements, they write, may “provide the promise of improved local control and quality of life in a carefully chosen multidisciplinary approach.”
Du, KL et al. “Extrapleural pneumonectomy, photodynamic therapy and intensity modulated radiation therapy for the treatment of malignant pleural mesothelioma”, September 8, 2010, Cancer Biology & Therapy. Published online prior to publication. Allen, AM et al. “Fatal pneumonitis associated with intensity-modulated radiation therapy for mesothelioma”, July 1, 2006. International Journal of Radiation Oncology, Biology, Physics. pp 640-5. Allen, AM et al. “Restricted Field IMRT Dramatically Enhances IMRT Planning for Mesothelioma”, December 1, 2007, International Journal of Radiation Oncology, Biology, Physics. Pp. 1587-1592.