That is the conclusion of UCLA researchers who compared tomotherapy and 3D conformal radiation therapy (CRT) in 45 patients with advanced pleural mesothelioma over an 8 year period. Of the forty-five consecutive patients, 23 received 3D-CRT and the other 22 received tomotherapy. Kaplan-Meier analysis was used to calculate overall survival, the time it took for a tumor to start regrowing in the same place, and the time it took for metastatic tumors to start appearing outside of the treatment field.
Tomotherapy and 3D-CRT are both methods of delivering radiation into a mesothelioma tumor in a very precise way. Both methods rely on CT imaging for guidance and both deliver radiation in tiny individual beams directed from multiple points around the body. While the two types of radiotherapy are similar, there are subtle differences, including the fact that tomotherapy is integrated with the CT scanner so that treatment sessions can be changed on a daily basis if a mesothelioma tumor grows or changes shape.
According to the UCLA team, this small difference appears to have a big impact on the way mesothelioma recurs after surgery. In the patients who had tomotherapy, it took a median of 19 months for mesothelioma tumors to start growing back in the original spot. For those who had 3D-CRT, the median time to local failure was only 10.9 months.
Although tomotherapy allowed more radiation to “leak” into the surrounding lung than 3D-CRT did, it also allowed 100% of the prescribed radiation dose to enter the tumors and the toxicity rates for the two methods were the same.
But it was not all good news for tomotherapy and mesothelioma. The mesothelioma patients who had 3D-CRT were significantly less likely to experience metastatic tumors (which the researchers called “out-of-field failures”) than those who had tomotherapy, which means they traded one set of problems for another. Most importantly, overall survival for the two radiotherapy methods was not significantly different.
The research team included thoracic surgeon and renowned mesothelioma specialist Dr. Robert Cameron, director of UCLA’s Mesothelioma Comprehensive Research Program.
Kishan, Amar et al, “Tomotherapy improves local control and changes failure patterns in locally advanced malignant pleural mesothelioma”, August 1, 2015, Practical Radiation Oncology, Epub ahead of print