"This approach is safe and can achieve a high rate of tumor control," presenter Eric Chang, MD, from the University of Texas MD Anderson Cancer Center, in Houston, said during an interview. "The effect was a bit more dramatic than we anticipated we might see," he noted.
Presenting at the plenary, Dr. Chang showed that stereotactic body radiosurgery achieved a 90% progression-free survival at 6 months and 84% at 1 year. "It can also lead to significant reductions in the amount of pain patients experience," he said.
An estimated 40% of all cancer patients will develop spinal metastases. These patients typically present with pain and possible neurological complications. Conventional irradiation has been useful for palliation, but its effectiveness can be limited by spinal-cord tolerance. Another problem is that reirradiation by conventional means is not possible.
Stereotactic body radiosurgery is an emerging technique that uses image guidance to deliver radiation and create a steep dose gradient between the spinal cord and tumor.
Emerging Technique
Asked by Medscape Neurology & Neurosurgery to comment, Michael Fehlings, MD, from the Toronto Western Hospital, in Ontario, called this "an attractive modality" and suggested that the rates of spinal metastases in cancer patients may be even higher than 40%.
Dr. Fehlings said that while these results appear promising, they are based on a small series, and he looks forward to the results of larger studies. The single-institution study was not randomized and had no control group.
Investigators evaluated 121 patients. They completed magnetic resonance imaging of the spine within 30 days of enrollment, every 3 months for the first year, and every 6 months after that. The researchers used the Brief Pain Inventory and the MD Anderson Symptom Inventory to assess patients at baseline and at each follow-up.
Patients underwent intensity-modulated, near-simultaneous, computed-tomography (CT) image-guided stereotactic body radiosurgery. They received 3 separate 9-Gy fractions to a total dose of 27 Gy. Investigators limited the spinal cord dose to 9 Gy.
Cancer types included renal cell, breast, sarcoma, lung, melanoma, and colon. The median tumor volume was 40.6 cm3. At the time of analysis, 39% of patients were alive with a median follow-up time of 13 months. The median survival time of the study population was 21.4 months.
The top 5 most severe symptoms patients reported were fatigue, pain, sleep disturbance, drowsiness, and distress. At 6 months, investigators said these symptoms declined.
Decreases in Symptoms at 6 Months
| Symptom | Reduction on MD Anderson Symptom Inventory | P |
| Fatigue | -0.7 | .03 |
| Pain | -1.6 | .001 |
| Sleep disturbance | -1.2 | .0001 |
| Drowsiness | -1.3 | .0001 |
| Distress | -1.0 | .0004 |
Dr. Chang and his team showed that acute toxicities were infrequent and manageable. There were no cases of grade 4 toxicities, but some grade 3 problems did occur. These included nausea, vomiting, diarrhea, fatigue, noncardiac chest pain, dysphagia, neck pain, and pain associated with severe tongue edema and trismus. No cases of radiation myelopathy have been observed to date.
Discussant Phillip Tibbs, MD, from the University of Kentucky, in Lexington, congratulated the researchers on the work. "Stereotactic body radiosurgery has a promising role in managing pain and controlling metastasis," he said at the meeting.
"I can tell you that at the University of Kentucky we are using it now," Dr. Tibbs noted. "It is a wonderful tool, and I think sometimes enthusiasm can lead to overuse. But I believe we have identified an appropriate indication for a suitable group of patients."
Dr. Tibbs pointed out the symptom inventories used in the study are subjective. "But I don't think that's a particular limitation here, and patient perception is appropriate."
The researchers have disclosed no relevant financial relationships.
American Association of Neurological Surgeons 77th Annual Meeting: Abstract 900. Presented May 6, 200
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