Intensity modulated radiation therapy (IMRT) can safely slow or even stop mesothelioma progression after surgery as long as the dose is just right. A team of Texas radiation oncologists reached that conclusion after studying the treatment results of 18 mesothelioma patients between 2005 and 2014.
IMRT is a highly targeted form of high-dose radiation. While it can have a powerfully negative effect on tumor cells, it can also have an equally negative effect on healthy lung tissue. Some patients have even died from pulmonary toxicity caused by IMRT.
But in a report published in the journal Oncology, doctors from Texas A & M Medical Sciences Center and Baylor Scott and White Hospital found that, as long as the radiation dose is kept within a certain range, IMRT can help keep mesothelioma from coming back after extrapleural pneumonectomy (EPP) while still preserving healthy lung function.
The 18 mesothelioma patients in the study each underwent EPP, a radical surgery that removes the diseased pleural membrane, as well as the effected lung, all or part of the diaphragm, the lining around the heart, and other tissues as risk for the spread of mesothelioma. Each patient then received IMRT to the one side of the chest as well as to the surgical incision site and the site where a chest tube was inserted. These sites are common places for mesothelioma cells to take hold again after surgery.
Four of the mesothelioma patients had had chemotherapy prior to surgery and another seven had it afterward. Fifteen of the patients had either stage II or stage III mesothelioma, while three had the most advanced stage IV. The highest IMRT dose that any of the patients received was 9.3 Gy and the lowest was 5 Gy. On average, about 2.23% of patients’ normal lung tissue absorbed a dose of radiation.
Keeping the radiation dose to the remaining lung low, while still treating the surgical area appeared to pay off. Three years after treatment, 8 of the patients were still alive. The median overall survival of all patients in the study was 38.2 months and the median time until mesothelioma started to spread again after treatment was close to two-and-a-half years — at least a year and a half longer than average mesothelioma survival.
Just as importantly, there were no grade 3 toxicities and none of the mesothelioma patients in the study died as a result of the IMRT treatment. In his summary of the findings, study author Sameer Jhavar, MD, of Texas A & M concludes, “In our patient population, strict adherence to lung dose constraints during IMRT resulted in improved outcomes without fatal toxicity.”
The results of the study were presented to the members of the American Radium Society at its annual convention in March.
Jhavar, Sameer, “Intensity-modulated radiation therapy after extrapleural pneumonectomy with and without chemotherapy for malignant pleural mesothelioma: no fatal pulmonary toxicity and long-term survival”, April 21, 2015, Oncology.