[Original article: biotechnologyfocus.ca ] [ Written by: Paul DeJean ]
Radiation therapy is a time-tested technique for controlling solid tumours in patients. Intensity modulated radiation therapy was a huge leap forward for radiation oncology, allowing for the precise delivery of radiation to tumour targets, sparing healthy tissue.
A linear accelerator (linac) delivers a carefully calibrated beam of radiation from one position, rotates around the patient, and delivers another beam, repeating the process hundreds of time to build up a dose distribution that converges on the tumour, while spreading out the burden to healthy tissue. Intensity-modulated radiation therapy is now the standard of care within Ontario. However, the tumour can change shape between radiation fractions, or move between imaging and treatment, so some healthy tissue must be sacrificed to create margins-of-safety.
Adding imaging capabilities in the form of a cone beam CT (CBCT) to create image guided radiation therapy (IGRT) allows the treatment team to identify the tumour in its exact position while the patient lies on the treatment bed. Therapy can be made even more conformal, ensuring that no tumour is missed and minimizing the damage to healthy tissue. The Princess Margaret Cancer Centre has been a leader in the research, development, and clinical adoption of IGRT. Researchers there have been optimizing this technique for clinical use for over a decade.
For research purposes, it would be ideal to mimic the clinical situation—including IGRT techniques—as closely as possible in preclinical models, to get the best results in understanding the mechanism of cancer control and to test novel therapies. However, preclinical radiation therapy simulation was limited to large box irradiators that delivered whole-body radiation fields to test specimens. This limited the scope of radiation therapy experiments.