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Researchers report reduced side effects with intensity-modulated radiation therapy


Researchers at the University of Pennsylvania report they were able to reduce the potentially fatal side effects of intensity-modulated radiation therapy in a small cohort of mesothelioma patients.


Intensity-modulated radiation therapy, or IMRT, is a relatively new technique typically used in conjunction with chemotherapy following extrapleural pneumonectomy, or EPP, a surgery that removes the tumor and lining of the lung where the tumor is located. It relies on computer-controlled linear accelerators to deliver radiation to the post-operative area, allowing for higher doses that destroy remaining cancer cells and less collateral damage to healthy tissues and organs.


However, while IMRT can improve outcomes in patients, previous research has showed that the higher doses increase the risk of radiation-induced pneumonitis, a potentially fatal inflammation of the lungs. Studies also suggest higher doses can prove more toxic to patients receiving chemotherapy.


At Penn, researchers are experimenting with a novel multi-modal approach using EPP, IMRT and intraoperative photodynamic therapy, which kills cancer cells by subjecting them to certain light frequencies using photosensitizing drugs activated by a laser.


In the September 2010 issue of Cancer Biology & Therapy, the researchers describe a study involving 11 patients with pleural mesothelioma who underwent EPP, followed by post-operative IMRT. Seven patients underwent intraoperative photodynamic therapy, while three who showed evidence of recurring disease received a pemetrexed-cisplatin chemotherapy regimen. (One patient did not complete IMRT.)


They report that only one patient, who did not undergo intraoperative photodynamic therapy, experienced respiratory failure due to radiation-induced pneumonitis. The patient did not require mechanical ventilation and the condition was successfully treated with steroids. Another patient whose disease had progressed experienced respiratory failure eight months after IMRT, but did not exhibit signs of pneumonitis or pulmonary fibrosis (scarring of the lung).


Acknowledging the small cohort in the study, the researchers say their results “preclude any significant statistical analysis,” adding that more research is needed to improve dose delivery and reduce lung toxicity.


However, they conclude that their approach may help prevent the spread of mesothelioma, while improving the quality of life of mesothelioma patients as they continue treatment.


“Our data demonstrate that combined treatment of patients with EPP and [intraoperative photodynamic therapy] followed by hemothoracic chest wall IMRT can be performed with acceptable toxicity,” they wrote.