Stereotactic body radiation superior to conventional radiation for spinal tumors
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Stereotactic body radiation therapy appeared more effective than conventional radiation in alleviating pain from spinal tumors, according to a Canadian Cancer Trials Group phase 2/phase 3 study presented at the virtual ASTRO Annual Meeting.
Researchers found that more than twice as many patients treated with SBRT reported a complete reduction in pain at the tumor site.
“This is the first randomized phase 3 trial to show that dose escalation with modern radiation therapy techniques improves pain outcomes for patients with spinal bone metastases,” Arjun Sahgal, MD, professor and deputy chief of radiation oncology at Sunnybrook Health Sciences Center at University of Toronto, said during a press conference. “Spine stereotactic body radiation is superior to conventional radiation and achieved a 21% absolute increase in complete response to pain at 3 months, which was durable at 6 months and statistically significant.”
There is no definitive standard-of-care radiation therapy dose to treat painful spinal metastases, which occur in as many as 70% of patients with terminal cancer, according to research.
Sahgal and colleagues sought to evaluate the role of conventional low-dose radiation therapy vs. high-dose SBRT for spinal metastases pain among 229 patients with primary tumors that metastasized to the spine.
“This was an initial phase 2 randomized controlled trial that was converted to a phase 3 randomized controlled trial without interruption of accrual,” Sahgal said. “Once we showed that we could accrue in the phase 2 portion, we received the approval to accrue to a phase 3 trial between January 2016 to September 2019.”
Researchers used the Brief Pain Inventory to assess eligible patients who reported initial pain scores of greater than two on a scale of one to 10. Pain scores were then measured at 3 months and 6 months.
The investigators randomly assigned patients 1:1 to SBRT dosed at 24 Gy in two fractions (n = 114) or conventional radiation therapy dosed at 20 Gy in five fractions (n = 115).
Complete pain response rate at 3 months served as the primary endpoint.
Complete response at 6 months, radiation site-specific PFS at 3 and 6 months, quality of life, change in total spinal instability and neoplasia score at 3 and 6 months, and OS served as secondary endpoints.
Four patients in the SBRT group did not receive study treatment. Sixteen patients in the SBRT group and 22 patients in the conventional radiotherapy could not be evaluated at the 3-month endpoint.
“This was an intention-to-treat analysis, but the safety and quality assurance analysis was based on as-treated,” Sahgal said.
Median follow-up was 6.7 months.
Among the evaluable patients, a higher percentage of those assigned SBRT reported a complete response — or no remaining pain from their lesions — at 3 months (35% vs. 14%; P < .001) and at 6 months (32% vs. 16%; P = .004).
Mean change in total spinal instability and neoplasia score at 3 months was –0.94 (standard deviation [SD], 1.69) with SBRT and –0.49 (SD, 1.61) with conventional radiation, and at 6 months was –0.74 (SD, 1.99) vs. –0.73 (SD, 1.86).
Researchers observed no significant differences in radiation site-specific PFS or OS between the groups. At 3 months, 92% of patients assigned SBRT and 86% of patients assigned conventional radiation were cancer-free at the treated site (P = .04), whereas 75% and 69% were cancer-free at 6 months (P = .04).
Results of multivariable analyses for complete response for pain that adjusted for age, sex, performance status, pain score at baseline, primary cancer type and total baseline spinal instability and neoplasia score showed a 3-month OR of 3.47 (95% CI, 1.77-6.8) and a 6-month OR of 2.45 (95% CI, 1.28-4.71) with SBRT.
“The complete response was highly significant at both endpoints. Therefore, it is an independent factor inducing complete response rate for pain,” Sahgal said.
No treatment-associated deaths occurred in either group and rates of serious adverse events were low, Sahgal added.
“Our regimen of 24 Gy in two stereotactic body radiation fractions was safe, non-destabilizing and associated with better patient financial perception,” he said.
Perspective
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Jessica Karen Wong, MD, MEng
Patients with metastatic cancer often present with painful metastases to the vertebral bodies that require radiation for symptom improvement. SBRT increasingly has been used for these patients for treatment intensification, with retrospective series suggesting superior local control and pain improvement compared with conventional radiation. The study by Sahgal and colleagues directly compared SBRT to the spine dosed at 24 Gy in two fractions with conventional palliative radiation dosed at 20 Gy in five fractions. Results showed that treatment with SBRT led to durable improvements in pain control with no increased toxicity. This is the first phase 3 randomized controlled trial to show that treatment intensification with modern SBRT improves pain outcomes for patients with painful spinal bone metastases, and the results support the adoption of this treatment as a standard of care.
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Sahgal A, et al. Abstract LBA-2. Presented at: American Society for Radiation Oncology Annual Meeting (virtual); Oct. 25-28, 2020.
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