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Clinical Study From Canada's McGill University Health Centre Shows TomoTherapy Technology Benefits for Use in Both Standard and Complicated Pediatric Cases

TomoTherapy Incorporated , maker of advanced radiation therapy solutions for cancer care, cited results of a study from McGill University Health Centre (MUHC) in Montreal, Quebec, Canada, that showed the benefits of TomoTherapy technology in a variety of cases requiring craniospinal irradiation (CSI) in children and young adults. The study -- entitled "Standard and Nonstandard Craniospinal Radiotherapy Using Helical TomoTherapy" and published online (Int J Radiat Oncol Biol Phys., March 2010; Epub ahead of print) -- concluded that the TomoTherapy platform offers a major dosimetric advantage in treating both standard and complicated cases by utilizing integrated daily imaging and helical radiation delivery to more accurately target tumors and spare surrounding structures and organs.

As reported in the study, "Helical TomoTherapy delivers continuous arc-based [intensity-modulated radiation therapy] (IMRT) that gives high conformality and excellent dose homogeneity for the target volume. Helical TomoTherapy allows for differential dosing of multiple targets resulting in very elegant dose distributions. By its conformal nature, IMRT is very sensitive to improper patient setup. The use of pretreatment [megavoltage CT] (MVCT) imaging with [helical TomoTherapy] allows for increased precision with respect to patient positioning and use of a reduced [planning target volume] (PTV) margin. Daily imaging of our patients has shown the technique to be very reproducible. We conclude that [helical TomoTherapy] is an excellent tool for planning and delivery of conformal IMRT for both standard and nonstandard CSI."

The McGill study focused on four patients, three of whom had complicating circumstances, such as unusual anatomy, prior radiation treatment or multiple boost targets. The first was a standard case of CSI in a 19-year-old patient with recurrent myxopapillary ependymoma (MPE). Two other patients received non-standard CSI via differential dosing -- one was a seven-year-old with recurrent medulloblastoma who had been treated before and required a simultaneous dose reduction to the posterior fossa, and the other was a 14-year-old with metastatic tumors throughout the craniospinal axis from MPE who required concurrent boosting of multiple sites. The fourth patient was a 21-year-old with neurofibromatosis and pronounced scoliosis who needed treatment of the whole spine for recurrent MPE.

"There exist major dosimetric advantages over conventional techniques," the study noted. "Lacking from the [helical TomoTherapy] plan is the hotspot created in the abdomen when using traditional skin gap junctioning techniques for the posterior spine. In addition, the [TomoTherapy] plan is significantly better in terms of maximum dose delivered. In fact, the plan maximum dose is 106%, which occurs within the patient treatment volume. Because of the use of direct fields and prescription points that can be at several centimeters' depth, it is not uncommon to see hotspots on the order of 130% posterior to the spinal cord and outside of the target volume when using conventional CSI techniques."

For the patients in the study, clinicians were able to extend the length of the radiation fields up to 60 cm to 90 cm with TomoTherapy technology, compared to field lengths of up to only 40 cm for standard radiation therapy solutions. This capability of the TomoTherapy system to create long fields means the entire craniospinal axis can be treated with a single set-up, thereby "obviating the risks associated with use of abutting fields, junctions and beam gaps," as the study reported. In addition, accurate patient setup via integrated MVCT imaging enables a margin reduction, which enables sparing of more healthy tissue.

All patients in the study received treatment while lying on their back, with a standard thermoplastic mask used for immobilization. Beam-on time ranged from 10-15.7 minutes and total time on the treatment table was typically 45 minutes for adult patients and 30 minutes for children. This is similar to, or less than, conventional treatment times.

"This study of CSI with helical TomoTherapy technology at McGill is an excellent example of the use of our system for the types of treatment for which it is uniquely suited," said TomoTherapy CEO Fred Robertson. "We are pleased that TomoTherapy can help pediatric and young adult patients, who may otherwise face limited treatment options because of prior radiation or other complicating factors."

Source: TomoTherapy Incorporated