March 10, 2010 - While intensity modulated radiation therapy (IMRT) can create a treatment that maximizes dose to the target and minimizes dose to healthy tissues, it can lead to longer delivery times compared with standard radiation therapy. That is prompted several radiation therapy centers around the world to adopt volumetric modulated radiation therapy (commonly known as VMAT), in which a single or multiple radiation beams sweep in uninterrupted arc(s) around the patient, significantly reducing treatment times.
At the Clinique Claude Bernard’s Private Radiotherapy Center of Metz (PRCM) in Metz, France, which installed and started using the Elekta VMAT system, clinicians found the average VMAT was much faster than IMRT.
“After only five months we were using VMAT to treat an average of 70 patients per day in an 11 to 12-hour day. At six months, almost everything apart from breast cancer cases was being done with the VMAT technique. Most importantly, the reduction in the length of treatment sessions is striking when compared to standard IMRT. VMAT treatment session times averaged half as long as those of IMRT," said Guillaume Faure, M.D., co-director of radiation oncology at PRCM.
A VMAT treatment session consists of pre-treatment image guidance time, patient set-up time and “beam-on time,”—the latter is when radiation is applied to the target. Depending on several factors, pre-treatment image guidance and set-up times can lead to treatment sessions ranging from five to nine minutes. Therefore, PRCM adopted an average treatment session time of seven minutes for all cases. Because VMAT beam-on time for all indications measures in tens of seconds, it now contributes less significantly to the total treatment session time. At PRCM, average VMAT beam-on times for five major indications are: 102 seconds for head-and-neck; 98 seconds for brain; 81 seconds for rectum; 79 seconds for prostate; and 79 seconds for lung.
VMAT beam-on time across these five case types is just 88 seconds. Compared with total treatment session times for IMRT, an average VMAT treatment session (seven minutes) is typically twice as fast. Examples include prostate IMRT at 14 minutes; head and neck IMRT at 22 minutes and rectal IMRT at 11 minutes.
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