Stereotactic Body Radiotherapy Effective for Treating Spine Tumors

Stereotactic body radiotherapy (SBRT) is a highly effective alternative treatment for some cancer patients with spinal metastases, according to new research from The University of Texas in Houston.

Eric L. Chang, M.D. The University of Texas in Houston

Dwight E. Heron, M.D. University of Pittsburgh Cancer Institute

For patients treated with SBRT, researchers found that the six-month and one-year progression-free survival rates for spinal metastasis were 90 percent and 84 percent respectively, according to the study's lead author Eric L. Chang, M.D., an associate professor in the Department of Radiation Oncology and director of the central nervous system stereotactic radiation program at the university's M.D. Anderson Cancer Center. Patients involved in the trial also reported reductions in pain, fatigue and sleep disturbances.

The study was presented at the American Association of Neurological Surgeons annual meeting in San Diego.

"SBRT offers patients a minimally invasive treatment option they previously did not have," said Dr. Chang. "We are also able to offer patients a degree of pain control and to decrease their pain medications, minimizing the side effects from those medications."

In the study, researchers evaluated 121 cancer patients with metastases to the spine who underwent intensity-modulated, near simultaneous, CT image-guided SBRT, said Dr. Chang.

Researchers used a stereotactic body frame system consisting of a whole-body vacuum cushion and plastic fixation sheet used to immobilize patients for the treatment period, which lasts approximately one hour.

The team performed MR imaging of the spine within 30 days of patient enrollment, every three months for the first year and every six months after that. Patients also evaluated their own pain and other discomfort using instruments including the validated Brief Pain Inventory and the M.D. Anderson Symptom Inventory.

Technique Controls Tumor Progression, Pain

Six months after treatment with SBRT, 90 percent of the patients were progression-free and one year after treatment 84 percent had no progression of spinal tumors, researchers found.

The method also proved to be effective in terms of pain control. At the trial's baseline, 27 percent of patients were pain-free. At three months, 50 percent reported being pain-free and at six months, 59 percent reported being completely pain-free.

Using CT image-guided stereotactic body radiotherapy (SBRT), the six-month and one-year progression-free survival rates for spinal metastasis were 90 percent and 84 percent respectively, researchers found. Previously irradiated T12 spinal metastasis from lung cancer showing biopsy-proven progression (note biopsy tract through the pedicle of the axial image of spine on the left). The re-irradiation treatment plan to deliver SBRT is shown in the axial, sagittal and coronal images. Images courtesy of Almon S. Shiu, Ph.D

Typical multiple co-planar beam arrangement utilized for delivery of SBRT for spinal metastases.

"We were surprised at how quickly the treatment began working," said Dr. Chang. "Within two to four weeks we could already see the reduction of pain pretty dramatically across the board in the patients we treated.

"The other surprising finding is that other areas of symptomatology were affected by this intervention as well," Dr. Chang continued. "Patients reported reduction in fatigue, drowsiness and sleep disturbances. No damage to the spinal cord was reported."

Dr. Chang said it is particularly encouraging to have SBRT as an option for patients who suffer from certain melanomas or renal cell tumors that often do not respond to conventional radiation therapy or for patients who have previously undergone radiation and are not candidates for further radiation treatments.

"The findings here are quite interesting and important, especially in the subgroup of patients who had prior radiation therapy to the spine," said Dwight E. Heron, M.D., an associate professor of radiation oncology at the University of Pittsburgh Cancer Institute (UPCI).

"We know in excess of 50 to 60 percent of patients who have cancer will develop bone metastasis over their lifetime," said Dr. Heron. "It can be fairly challenging, particularly if a patient has had radiation that is commonly used to treat the spine for palliation. If they have had radiation before, it's difficult to retreat the same or adjacent area a second time because the spinal cord can only tolerate a certain dose of radiation without significant toxicity.

"Our options after patients have failed a course of radiation are limited," Dr. Heron concluded. "We can treat them with a nerve block and then perhaps prescribe narcotics, but that usually has an adverse impact on the patient's overall quality of life."

Dr. Heron said he believes the M.D. Anderson prospective study corroborates the findings UPCI researchers have gathered retrospectively in their use of SBRT for spinal metastases in more than 750 patients.

Treatment Applications Could "Explode"

Drs. Chang and Heron feel the next step in this research is to collect more medical evidence so that insurance companies will consider SBRT a reliable treatment option.

The case for using SBRT is best made in a certain subset of patients whose histologies, like tumors from kidneys or certain skin cancers such as melanomas, tend to be a bit more resistant to conventional radiation, Dr. Heron said.

"In those cases, these higher doses of radiation may actually be more efficacious as the first attempt to control these tumors and offer patients pain relief," he said. "We need to show insurance companies that using this more expensive technology upfront before using the cheaper approach is better because you don't have to do a second course of radiation and because patients get pain relief. We can get them off narcotics and possibly avoid some spinal complications that we see in the more traditional approach."

Dr. Chang predicts a growing demand for the use of SBRT in clinical application. "I think application of this treatment could explode in the future because there is a large unmet need for this type of treatment."

In contrast to the relative ineffectiveness of conventional therapies, Dr. Chang said he and his team were encouraged to see a reduction in pain and growth in the so-called radio-resistant tumors.

"Our team has been frustrated in the past by how these radioresistant cancers can continue to grow after treatment with conventional radiation," he said. "When a particular treatment fails, patients want to know what options they have. If this technique is not available, they really don't have another option except surgery or palliative medicine. That's why we apply it to the most difficult cases to get the maximum benefit for patients."

Utilization Barriers Remain

Along with convincing insurance companies of its efficacy, cost and the small number of well-trained teams performing SBRT on the spine are current barriers to increased utilization of the methodology, Dr. Chang said. However, both he and Dr. Heron said they believe research results like those presented by M.D. Anderson and UPCI teams will create demand.

"I think as the technology gets better and the cost comes down, we may start looking at this as the primary way to treat radioresistant tumors," said Dr. Heron.

Drs. Chang and Heron agreed that changes involving increased use of SBRT must be considered thoughtfully.

Dr. Chang said he believes having a well-trained staff is essential to replicating the outcomes seen at M.D. Anderson. Dr. Heron stressed the importance of careful deliberation for each team considering SBRT for spinal metastases.

"I'm always cautious here," said Dr. Heron. "It's great to have great technology. At the same time, just because you have a hammer, doesn't mean everything you see is a nail."