RapidArc First Time Used For Soft Tissue Carcinoma Treatment

2008-07-23 10:57
RapidArc Radiotherapy Technology

MIMA Cancer Center becomes the firstirst in world to treat soft tissue carcinoma with stereotactic body radiotherapy using RapidArc Radiotherapy Technology from Varian. Novel image-guided treatment is completed in just five minutes a day for five days.

Doctors at Melbourne Internal Medical Associates (MIMA) Cancer Center have become the first in Florida to treat cancer using RapidArc™ radiotherapy technology from Varian Medical Systems (NYSE: VAR). They are also the first in the world to use this technology to deliver stereotactic body radiotherapy (SBRT) in the treatment of soft tissue carcinoma.

A 72-year-old man with Merkel cell carcinoma was treated for a soft tissue tumor in his thigh, which had developed close to where a similar tumor had been treated with conventional radiotherapy six months earlier.

"In this case, it was important that we avoid exposing the previously-treated area to any additional radiation," said Todd Scarbrough, M.D., radiation oncologist and director of the MIMA Cancer Center. "Using RapidArc, we completed each of his treatment sessions in just five minutes, including imaging and treatment. In the past, using conventional IMRT, this type of treatment would have required 30 minutes per session to complete."

RapidArc makes it possible to quickly deliver an advanced image-guided, intensity-modulated radiation therapy (IMRT) treatment with one 360 degree rotation of the treatment machine around the patient. In this case, however, Scarbrough and his team designed a treatment that was delivered with just half a rotation around the patient.

"The tumor was near the surface of his thigh, so a full arc would have exposed too much of his normal leg to the treatment beam," Scarbrough said.

Scarbrough's team planned the RapidArc treatment using Varian's Eclipse™ treatment planning software, which allowed them to visualize how the dose would be distributed within the patient's leg. "The RapidArc plan gave us a dose distribution that was superior to what we could have achieved with traditional IMRT," Scarbrough said. "Eclipse made it easy to create a plan that would avoid the previously-irradiated tissues. We just superimposed the dose distribution from his earlier treatments onto the new CT scans, created a structure out of that area, and instructed the software to avoid it as if it were a critical organ. It was very easy to do."

Stereotactic body radiotherapy involves delivering higher-than-usual doses of radiation to a tumor over a shorter-than-usual timeframe. It requires great accuracy and precision, both in terms of targeting and in terms of beam shaping, to minimize the exposure of surrounding tissues. MIMA's RapidArc protocol achieves the necessary level of precision. 3-D X-ray images of the targeted area are used to fine-tune patient positioning prior to each treatment. Then, as the treatment machine rotates around the patient, the treatment beam is continually shaped and reshaped to match the dimensions of the tumor.

"Any time you have a spherical lesion that is deep within the body, and you want to deliver a high dose, RapidArc is going to be the ideal way to treat," Scarbrough said. "Our plan is to use RapidArc any time the treatment plan gives us a dose distribution that is equal to or better than what we can get with standard IMRT, because RapidArc is so much faster. And that's much better for our patients." Scarbrough's team is now working on RapidArc treatment plans for a prostate and a lung cancer case scheduled to begin treatment later this month.

The American Cancer Society estimates that, in the United States this year, doctors will diagnose 1,437,180 new cancer cases; over 100,000 will occur in the state of Florida.

RapidArc radiotherapy technology is a major advance from Varian Medical Systems that improves dose conformity while significantly shortening treatment times. RapidArc delivers treatments two to eight times faster than our fastest dynamic treatments today and increase precision—a winning combination that enables physicians to improve the standard of care and treat more patients.
Volumetric modulated arc therapy

RapidArc is a volumetric arc therapy that delivers a precisely sculpted 3D dose distribution with a single 360-degree rotation of the linear accelerator gantry. It is made possible by a treatment planning algorithm that simultaneously changes three parameters during treatment:

* rotation speed of the gantry
* shape of the treatment aperture using the movement of multileaf collimator leaves
* delivery dose rate.

Volumetric modulated arc therapy differs from existing techniques like helical IMRT or intensity-modulated arc therapy (IMAT) because it delivers dose to the whole volume, rather than slice by slice. And the treatment planning algorithm ensures the treatment precision, helping to spare normal healthy tissue.

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