Stanford Study on CyberKnife Radiosurgery for Prostate Cancer Demonstrates 100 Percent PSA Response at 33 months

Prior Studies Demonstrate Frequency of Prostate Motion, Supporting Need for the CyberKnife System's Real-Time Tracking to Spare Surrounding Sensitive Structures

SUNNYVALE, Calif., March 31 /PRNewswire-FirstCall/ -- Accuray Incorporated (Nasdaq: ARAY), a global leader in the field of radiosurgery, announced today publication of the results from a prospective clinical study on CyberKnife radiosurgery for prostate cancer, which was published in the March 15, 2009 issue of the International Journal of Radiation Oncology*Biology*Physics - also known as the Red Journal.

The study, led by Christopher King, M.D. at the Stanford University School of Medicine, treated 41 low-risk prostate cancer patients using CyberKnife radiosurgery. Continual image guidance was used to verify target position throughout the procedure allowing the team to precisely deliver very high doses of radiation in five short treatments. At a median follow-up of 33 months, no patient experienced a PSA recurrence and early side effects were no worse than other prostate cancer therapies.

The authors refer to the findings as "highly encouraging," but remind readers that longer follow-up is required "to confirm durable biochemical control rates and low late toxicity profiles."

"The evidence in Dr. King's study shows a lot of promise for prostate cancer patients around the world who are looking for a shorter, less invasive and more convenient course of treatment," said Eric P. Lindquist, senior vice president and chief marketing officer at Accuray. "We look forward to seeing longer term results and study outcomes examining the side effect profile of CyberKnife radiosurgery. Doctor and patient experience thus far has been very positive."

Because the prostate can move unpredictably due to bowel gas or filling of the bladder, it is important that prostate motion is assessed and corrected for throughout treatment to allow for accurate radiosurgery treatment. Recent studies have confirmed that the prostate experiences rapid and unpredictable motion of as much as five millimeters in as few as 30 seconds, meaning that radiosurgery delivery must recognize and correct for even the slightest motion to ensure the target receives adequate dose and the surrounding sensitive structures, such as the rectum, bladder, urethra and nerves, are maximally spared.

In September 2008Accuray launched the InTempo(TM) Adaptive Imaging System, which enhances the CyberKnife System's ability to continually track and correct for motion of the prostate during treatment. With the InTempo System, CyberKnife radiation delivery automatically adapts to each individual patient's prostate motion by intelligently increasing the imaging frequency during periods of rapid and erratic prostate movement. This continual assessment of prostate motion, combined with the CyberKnife System's automatic correction for movement in real-time, not only helps to ensure prescribed doses are delivered to the prostate; it also helps to ensure surrounding structures are avoided, minimizing associated side effects and complications. Using the InTempo System, the CyberKnife System drastically minimizes the "image age" - or time between image capture and when individual beam delivery is complete - to as few as 10 seconds.

Conventional IGRT therapies and other "rapid" radiation delivery techniques typically provide imaging limited to only pre-treatment set-up and therefore lack the ability to recognize motion that occurs during treatment delivery. With such conventional techniques there is - at minimum - a two minute delay in the time between when the image is captured and the beam delivery is completed. With an image age of two minutes or more, potential motion that has proven to occur in as few as 30 seconds remains undetected, potentially resulting in inferior targeting accuracy and a heightened risk of surrounding tissue complications.

Another study, led by the Stanford University School of Medicine and published in the Red Journal'sSeptember 1, 2008, concluded the following in regard to prostate motion during radiation delivery; "Our study shows the importance of real-time image guidance and motion-compensation techniques such as the robotic linear accelerator used in CyberKnife during hypofractionated prostate radiation treatment. Given the magnitude and random nature of prostate motion as well as recent technical advancements in various related fields, real-time monitoring of prostate position to compensate for the motion should be part of future prostate radiation therapy to ensure adequate dose coverage of the target while maintaining adequate sparing of adjacent structures."

About the CyberKnife(R) Robotic Radiosurgery System

The CyberKnife Robotic Radiosurgery System is the world's only robotic radiosurgery system designed to treat tumors anywhere in the body non-invasively. Using continual image guidance technology and computer controlled robotic mobility, the CyberKnife System automatically tracks, detects and corrects for tumor and patient movement in real-time throughout the treatment. This enables the CyberKnife System to deliver high-dose radiation with pinpoint precision, which minimizes damage to surrounding healthy tissue and eliminates the need for invasive head or body stabilization frames.

About Accuray

Accuray Incorporated (Nasdaq: ARAY), based in Sunnyvale, Calif., is a global leader in the field of radiosurgery dedicated to providing an improved quality of life and a non-surgical treatment option for those diagnosed with cancer. Accuray develops and markets the CyberKnife Robotic Radiosurgery System, which extends the benefits of radiosurgery to include extracranial tumors, including those in the spine, lung, prostate, liver and pancreas. To date, the CyberKnife System has been used to treat more than 60,000 patients worldwide and currently more than 155 systems have been installed in leading hospitals in the Americas, Europe and Asia. For more information, please visit www.accuray.com.

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SOURCE Accuray Incorporated

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