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Treating tumors and inoperable growths in the spine is a delicate task that requires comprehensive planning. Typically the location of these lesions is in close proximity to vital organs and the risks from surgery or radiation tend to nullify the benefits. Fortunately, a novel technique known as stereotactic body radiation therapy (SBRT) is providing clinicians a way to deliver powerful radiation to tumors that are not amenable to traditional methods.

SBRT is an ablative procedure which applies targeted radiation to the body similar to the way a gamma knife delivers precise radiation to the brain. Using a fusion of different technologies and specialties, patients are kept immobilized while particular areas of the body receive high-powered, hypofractioned radiation in a 360 degree delivery. This precise delivery system allows a reduction in radiation treatment time for some early stage tumors from multiple weeks to just a single or a few days, especially oligometastases in lung, liver, and bone. SBRT can also benefit benign lesions such as hemangiomas and spinal meningiomas.

“This is an exciting therapy in that it’s minimally invasive and has few side effects,” said Dr. Michael Farmer, radiation oncologist at Methodist University Hospital. The team overseeing the technique consists of a radiation oncologist, neurosurgeon, and physicist. “For the inoperable patient or one who can’t tolerate surgery, it opens up a new treatment possibility.”

Physicians have traditionally used surgery, conventional radiation or a combination of both for patients with spinal tumors. For instance, a single spine metastasis is often dealt with surgically at the outset. Conventional radiation does not allow for highly accurate delivery but can be effective in some cases. SBRT opens the door to treating those lesions that were previously deemed untreatable either due to radiation sensitivity or resistance, or the tumors that were inoperable due to co-morbidities in the patient.

The biggest challenge for the technique is full immobilization. Unlike with the brain, keeping the body as immobilized is unfeasible, not only because it’s a non-rigid surface but it’s also associated with substantial organ movement. Utilizing the latest in immobilization technology does allow Farmer to keep patients immobilized within two to three millimeters, ensuring minimal radiation to normal tissue. Studies are ongoing to develop and implement the best available immobilization techniques.

Used as an adjunct to surgery, SBRT can reduce a large surgery to a smaller procedure. In some cases it can even be an alternative to surgery, although not everyone is an anatomically and geometrically ideal candidate. Patients must have a minimal estimated survival time of six months and the tumor cannot be more than six centimeters in size.

“It is difficult to take care of metastatic spine disease in a comprehensive manner without stereotactic radiation,” explained Dr. Jason Weaver, neurosurgeon with Semmes-Murphey Clinic.

In fact, he said, “it’s difficult to treat those lesions as aggressively as we’d like.”

SBRT provides long term, local control. This spinal stabilization, explained Weaver, essentially slows the progression of the disease which translates to a greater quality of life for patients by reducing incapacitating side effects like pain, incontinence, bone fracture and paralysis. In combination with surgery it is not impossible to potentially eliminate local spine disease.

Farmer and Weaver treated their first patient with SBRT in late December. It involved a large hemangioma that was highly radiosensitive. Instead of a large, complex surgery, the patient received SBRT and a small surgery which is expected to stabilize the anterior disease.

Weaver gave his patient an excellent prognosis because hemangiomas do not typically metastasize, he explained, and the stabilization of the disease will allow the patients’ body to generate normal bone in its place. Fortunately in this type of ideal situation, the tumor is unlikely to progress and will remain dormant for the remainder of the patient’s life.

The average number of procedures is about three, although some patients only need one, and SBRT is suitable for younger and older patients. Surgery or more radiation may be required in the future and patients need close monitoring of disease progression.

Some oncologists have been reluctant to send their metastatic patients to neurosurgeons, explained Weaver, because they think it is only about the surgery. But surgery is only one option, and, Weaver added, these patients should be followed very closely by a neurosurgeon along with their oncologist to determine the best course of treatment.

“This brings a much needed commodity to Memphis,” said Weaver. “We have an opportunity to develop a more comprehensive program for people with known spinal tumors, metastatic or primary.”

A collaborative effort of oncologists, neurosurgeons, radiation oncologists, pain specialists and general practitioners evaluating and treating metastatic cancer patients is an ideal goal Weaver said, that can take Memphis to a higher level of cancer care.



March 2008

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