This 1994 article describes Dr. Adler's invention; please see too more recent articles on Stereotactic Radiosurgery, such as Caution Urged for Stereotactic Radiosurgery, June 1998.

The first patient to receive frameless stereotactic radiosurgery with the Accuray Neurotron 1000 was treated June 8, 1994, at Stanford University with Dr. John Adler, neurosurgeon and Dr. Richard Hoppe, radiation oncologist. The Neurotron 1000 is a robot machine which brings some significant advancements to the field of stereotactic radiosurgery.

Stereotactic radiosurgery is a method for stunting the growth of a tumor without conventional surgery. Laser-beams of radiation are aimed at the "target site," the tumor, from hundreds of different angles. As each beam passes through healthy tissue, that tissue gets the low one-beam dose. Where the hundreds of beams come together at the tumor, the tumor receives the sum of the dosages of all those beams, effectively performing laser surgery on the tumor.

Stereotactic radiation is still somewhat controversial in the neurosurgical community. Conventional microsurgery is still considered the first choice for tumors of the cerebellum, where surgical risks are relatively low. Times when you might consider stereotactic radiosurgery¹ are

- When the tumor is deep in the brain- When there are recurrent tumors- Where there are multiple tumors which cannot all be handled in one surgery- Where the patient is frail and would not tolerate conventional surgery very well

- For preventive treatment of small asymptomatic tumors, before they develop a cyst

The best candidates for stereotactic radiosurgery are tumors which are 2-3 cm. in size. If there is an associated cyst, it will not get better quickly, but will shrink over some months. Sometimes a shunt or other method of shrinking the cyst can be used in combination with radiosurgery to manage the cyst.

A number of VHL patients have undergone stereotactic radiosurgery for treatment of hemangioblastomas of the brain, and are generally delighted with the procedure. There are many treatment centers around the country using either gamma knife or linear accelerator machines.

David I. of California recently underwent gamma knife stereotactic radiosurgery treatment at Stanford for his second VHL hemangioblastoma. The first was successfully treated with conventional surgery. "I am tempted to say it was fun," he says, "but that is not the right word. It certainly was interesting and relatively painless."

My appointment was for eight o’clock and by 10:30 my wife and I were having brunch at a nearby restaurant! I looked at her across the table and said, ’Do you realize I just had brain surgery?’ We found the thought almost amusing. I had two small bandaids on my forehead where the frame had been attached and other than that, the casual observer would have no way to telling there was anything unusual about me. I had no aftereffects from the surgery, no nausea, no headache. I felt as well as I had going in that morning, I even stopped in at my office and visited and will be returning to work this morning. And I had brain surgery yesterday morning!"

Using today’s treatment machines, the patient must wear a "helmet" throughout the treatment which is screwed to the skull to keep it fixed in place. CT and MRI testing are used with the helmet in place to determine the precise relationship between the tumor and the frame. These measurements are then used during the treatment to aim the beams at the tumor.

Using "target tracking" software from the space and missile tracking programs, the Neurotron 1000 follows the target site and adjusts for patient movements up to 1 centimeter (one-third inch) and stops automatically if the patient moves more than that. This keeps the beam focused precisely on the "target" and eliminates the need for the frame.

It is possible to fix the frame to the bony skull and be confident that the tumor will stay in that fixed relationship to the skull. But there is no such bony structure which can be used to cause a rigidly fixed relationship around, for example, a kidney tumor. Up to this time, this has limited the application of this methodology mostly to brain tumors.

Dr. Adler has treated a number of VHL patients with hemangiomas of the brain, and is hopeful that the frameless treatment can be applied to spinal and kidney tumors as well. "While designed initially to treat cancerous tumors of the brain," Dr. Adler says, "the Neurotron 1000 system is also being designed for treatment of other body sites. This achievement has the potential to dramatically change the treatment of many solid malignancies which represent the vast majority of cancers. Compared to alternatives, Accuray’s precision radiation treatment promises to be a more effective, less painful and less expensive therapy for many cancer patients."

Today’s machines move in only one or two planes, so that they deliver a spherical dose. If the tumor is not spherical, but is irregular in shape, overlapping spherical doses to cover the tumor result in some areas of undertreatment, and some of overtreatment. As a result, not all irregular tumors can be treated today with stereotactic radiosurgery.

The Neurotron 1000 moves on six planes or axes, which allow it to plan a dose distribution the shape of the tumor and treat the entire tumor area evenly.

This project has been funded in part by the Murray Foundation, with the express intent of creating advancements which will facilitate treatment without invasive surgery of VHL hemangioblastomas of the brain, spine and other organs. "People with VHL," says Mike Murray, "often have to deal with a series of invasive surgeries which themselves take a physical and mental toll on the human being. The Neurotron 1000 will provide a non-invasive approach to treating many of these tumors until we have a genetic treatment or cure for VHL."

This machine is also expected to lead to reductions in the cost of treatment by making it possible to treat more patients in the same length of time. Today, the treatment team is intensely involved with a single patient during an elaborate setup procedure which has to happen after the fixing of the frame. With the Neurotron 1000, the CT’s and MRI’s can be done in advance so that the time in the treatment room is minimized.

Dr. Joseph G. Depp, president and CEO of Accuray,2 stated, "The first patient treatment officially launches clinical trials which are required by the FDA before commercial marketing of the system can commence in the United States. During the next few months, Accuray will be installing additional prototypes at Newport Diagnostic Center in Orange County, California; Simmons Cancer Center at the University of Texas in Dallas; Shadyside Hospital in Pittsburgh, Pennsylvania; Georgetown University Medical Center in Washington, D.C.; and the Cleveland Clinic in Cleveland, Ohio. A prototype will also be installed by Marubeni in Japan to provide clinical data for Japan’s Ministry of Health."

1. For an excellent laymen’s explanation of central nervous system hemangioblastomas and surgical options, see Advances in Treatment of CNS Lesions, a presentation by Dr. Haring J.W. Nauta, University of Texas Medical Units, Galveston, and Dr. John Adler, Stanford University Medical Center, on the audio tapes of the VHL Family Alliance meeting in Kansas City, April 1994. See page 15 for ordering information. 2. Accuray, 1715 Wyatt Drive, Santa Clara CA 95054 (408) 982-9900.

As published in the VHL Family Forum 2:3, September 1994. For permission to reprint, please contact the VHL Family Alliance at editor@vhl.org. Further information is available from the VHL Family Alliance, info@vhl.org.