RADIATION THERAPY FOR MALIGNANT PLEURAL MESOTHELIOMA
Treatment of malignant pleural mesothelioma with radiation therapy (RT) is extremely challenging. The target volume for treatment is very large, involving almost the entire hemithorax, and within and adjacent to this treatment volume, there are many normal structures with low tolerances to radiation. Consequently, it is very difficult to create treatment plans that deliver therapeutic doses to the tumor target volume while respecting normal tissue tolerances. This chapter reviews the history, current approaches, and future ideas for the treatment of malignant pleural mesothelioma with radiotherapy in definitive, adjuvant, and palliative settings.
Definitive Radiation Therapy Alone for Mesothelioma
For the treatment of unresected gross disease, the target volume for RT includes the entire visceral and parietal pleura of one lung. These structures form a circumferential envelope around the lung, extend along fissures between lobes of the lung, and are attached to ipsilateral, pericardial, and diaphragmatic surfaces. A typical definitive dose of RT for gross disease of all types is 60 Gy, but the tolerable dose to the adjacent organs such as lung, heart, and liver is often limiting.1
Few reported series address the definitive treatment of unresected pleural mesothelioma, and none shows promising results. Alberts et al. reported outcome for 262 patients treated with various combinations of RT, pleurectomy, and chemotherapy.2 RT was delivered to the entire hemithorax with doses of 45 to 80 Gy. All treatment groups had similar outcomes, with a median survival time of 9.6 months.
Ball and Cruickshank reported on a series of 35 patients treated with RT at the Peter MacCallum Institute, 12 of whom received radical RT to a total dose of 50 Gy.3 There were two treatment-related fatalities (17%) due to radiation hepatitis and radiation myelopathy, respectively, and median survival was 9 months.
More recently, Memorial Sloan-Kettering Cancer Center (MSKCC) reported on 39 patients who either were unresectable or underwent partial pleurectomy and received IMRT. Patients received chemotherapy and a definitive dose of RT. The median time to local failure was 6 months, with 1- and 2-year actuarial local failure rates of 66% and 83%, respectively. The median overall survival was an encouraging 22 months. The 1- and 2-year actuarial OS rates were 82% and 42%, respectively.4
Adjuvant Radiation Therapy for Mesothelioma
The Role of Radiation Therapy After Surgical Resection
There are limited data with regard to the use of radiation therapy as a standard treatment modality in mesothelioma. A retrospective review of 663 patients from three institutions demonstrated improved survival with the use of chemotherapy and/or radiation therapy with surgery compared to surgery alone.5
The role of radiation therapy has been questioned in a recent analysis of the Surveillance, Epidemiology, and End Result (SEER) database of 14,228 patients with mesothelioma.6...