Danish medical researchers have recently published the results of a study that investigated pulmonary toxicity following intensity-modulated radiotherapy (IMRT) in mesothelioma patients.
Intensity-modulated radiation therapy uses high-precision radiotherapy, via computer-controlled linear accelerators, to target a malignant tumor or areas of a tumor. This method delivers precise doses of radiation, and allows the radiation to conform to the shape of the tumor rather than targeting it one-dimensionally, as traditional external radiation methods do.
Twenty-six malignant mesothelioma patients were involved in the study, which took place at the national hospital of Denmark, Rigshospitalet, between April 2003 and April 2006. All of the patients underwent trimodality therapy consisting of induction chemotherapy, extrapleural pneumonectomy (removal of part of the lung and the mesothelium), and IMRT. After the extrapleural pneumonectomies, CT scans were performed on the patients to identify the remaining tumors and to map the organs at risk from radiation, which included the spinal cord, heart, liver, kidneys, esophagus, and contralateral lung (non-affected lung).
Pulmonary toxicity from the radiation technique was then measured. Some of the symptoms reported after the IMRT included nausea, vomiting, dyspnea (shortness of breath), thrombocytopenia (low levels of platelets in the blood and abnormal bleeding) and pneumonitis (inflammation of lung tissue).
Such lung toxicity can sometimes be fatal. According to the researchers in the Danish study, “the incidence of fatal radiation-induced pneumonitis…has been reported to be as high as six of 13 patients (46%) in a study from 2006 by Allen et. al. Subsequently, the incidence of fatal pulmonary complications was reported to be 10% in a series of 63 patients treated at the University of Texas M.D. Anderson Cancer Center…and 8% in a series of 13 patients treated at Duke University Medical Center.”
These results suggest that low doses of radiation to remaining lung tissue following surgery are a major contributor to lung toxicity. The researchers are therefore recommending a modification of lung dose constraints to avoid unacceptable levels of pulmonary toxicity as a result of trimodality therapy in malignant pleural mesothelioma patients.