Promising Early Local Control of Malignant Pleural Mesothelioma Following Postoperative Intensity Modulated Radiotherapy (IMRT) to the Chest

Malignant pleural mesothelioma often recurs locally in spite of aggressive resection by extrapleural pneumonectomy and conventional radiotherapy. This may be due to failure to recognize the extent of clinical target volume (CTV) or suboptimal dose delivery to a target that abuts the heart, esophagus, liver, lung, kidney, and spinal cord. We report how these geometric/dosimetric constraints were overcome by exploiting intensity-modulated radiotherapy in the first cohort patient.Twenty-eight patients who had undergone extrapleural pneumonectomy were treated with intensity-modulated radiotherapy. The CTV included the surgically violated inner chest wall, insertion of diaphragm, pleural reflections, and deep margin of the incision. CTV delineation was facilitated by intraoperative radio-opaque marking. Motion was assessed. CTV doses were 45-50 Gy with boosts taken to 60 Gy.Despite the large, irregular CTV (median, 4151 cc; range, 2667-7286 cc), an average of 97% of the CTV was covered to the target dose (range, 92%-100%). Respiratory motion was minimal because of immobility of the prosthetic diaphragm. Normal tissue dose constraints were met. The commonest effects were nausea/vomiting (89%) and dyspnea (80%). Esophagitis was absent (59% of patients) or mild (34% grade 1/2). At median follow-up of 9 months (range, 5-27 months), local control within the contoured target was 100%. One-year survival, disease-specific survival, and disease-free survival are 65%, 91%, and 88%, respectively.Intensity-modulated radiotherapy after extrapleural pneumonectomy is tolerable and seems effective, at least at this early point. As local control improves, systemic metastases become more common, and it may be appropriate to add novel agents to further improve the therapeutic ratio.