The rapid adoption of volumetric modulated arc therapy is generating a flurry of new treatment planning solutions.
By: Cristen C. Bolan

Since volumetric modulated arc therapy (VMAT) became available in the U.S., it has taken off in radiation oncology. The promise of VMAT delivery is to drastically cut treatment times compared to traditional IMRT. The shorter treatment times result in less patient movement, and thus increased accuracy and the potential to spare healthy surrounding tissue.

The adoption of VMAT is driving an influx of new VMAT-enabled tools to market, and leading the trend are new treatment planning solutions with arc-enabled modules.

From IMRT to VMAT
Taking IMRT to a new level, Elekta and Varian Medical Systems developed the first commercially available solutions providing volumetric-arc therapy. Elekta grabbed the acronym — VMAT — to brand its treatment solution, while Varian introduced its arc therapy solution RapidArc.

Treatment planning for Elekta’s system follows a similar approach to planning for conventional IMRT, but Elekta’s VMAT can be delivered using a single arc, multiple arcs, partial arcs, or a combination, depending on what the physician considers best for the patient. New VMAT tools enable users to create arc-based treatment plans using the same features available in Elekta’s Monaco solution. With reduced planning time and increased clinical throughput, Monaco with VMAT optimizes single or multiple non-coplanar arcs simultaneously.

“It’s fair to say there is a lot of interest around volumetric arc therapy. It likely will be widely adopted,” said Vivek Mehta, M.D., radiation oncologist, Swedish Cancer Institute, Seattle, Wash. “There are two drivers. One is it’s a much more efficient way of treating patients, because it shortens the time the patient has to spend on the table, and it reduces the dose to normal tissue. That’s what’s going to drive uptake.”

Redesigning Treatment Plans
The rapid uptake of VMAT is the force behind the development of new treatment-planning solutions programmed to include algorithms for volumetric arc therapy planning.

This year Philips launched SmartArc, an independent treatment planning solution for volumetric-modulated arc therapy (VMAT). Bundled as a module in Philips’ Pinnacle3 version 9 radiation treatment planning (RTP) software, the new planning option can be used with any VMAT-capable delivery system on the market. The system provides for constant-dose rate delivery designed to allow clinicians to explore the benefits of VMAT delivery without the expense and downtime associated with an upgrade to their linear accelerator.

Dr. Mehta uses IMRT or VMAT to treat patients with brain, head and neck, intra-abdominal tumors, such as pancreas, gastric, for prostate cancers and to treat patients that have been previously irradiated. SmartArc allows single or multiple user-definable arcs and supports both constant- and variable- dose rate delivery. The advantage of both constant- and variable-dose rate delivery is it “allows for improved planning and dose delivery, particularly for patients with complicated target volumes,” explained Dr. Mehta.

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