SBRT Appears to be Superior to CRT for Controlling Pain Related to Spinal Metastases

Stereotactic body radiotherapy (SBRT) may be superior to conventional palliative radiotherapy (CRT) in improving the complete response (CR) rate for pain related to spinal metastases at 3- and 6-months post-radiation, according to a randomized phase 2/3 trial presented at the American Society for Radiation Oncology (ASTRO) Annual Meeting.¹

Specifically, more than twice as many patients treated with SBRT reported an enduring, complete reduction in pain, compared to those treated with CRT.

“This is the first phase 3 randomized trial that has shown an improvement with dose escalation for painful spinal lesions,” lead author Arjun Sahgal, MD, a professor and deputy chief of radiation oncology at the Sunnybrook Health Sciences Centre of the University of Toronto, said in a press release.² “Pain deteriorates a patient’s quality of life and nobody with advanced cancer should have to endure this kind of pain. Patients with painful spinal metastases who meet the eligibility criteria should be offered this treatment.”

In this study, patients with a de novo site of painful spinal metastases were randomized 1:1 to receive either 24Gy in 2 SBRT fractions or 20Gy in 5 CRT fractions. Patients included in the study had a target site spinal metastases (≤3 consecutive metastatically involved spinal segments) arising from a solid primary tumor causing a pain score of 2 or more using the Brief Pain Inventory (BPI), an ECOG of 0 to 2, and were not mechanically unstable per the Spinal Instability Neoplasia Score classification system.

The primary end point for the study was CR rate for pain in the treatment area at 3 months post-radiation using International Consensus Pain Response Endpoints. Key secondary end points included the 6-month pain CR rate, radiation site progression-free-survival (RSS PFS) defined as the time from randomization to local progression or death, and quality of life (QoL).

Of the 229 patients enrolled between January 2016 and September 2019, 115 were randomized to CRT and 114 to SBRT of which 4 patients in the SBRT arm were either ineligible or withdrew prior to radiation. Moreover, 38 patients, including 22 in the CRT arm and 16 in the SBRT arm, were not evaluable for the primary end point.

The median baseline worst pain score was 5 (range, 2-10) and SINS was 7 (range, 3-12) in both arms. Median follow-up time was 6.7 months.

At 3 months, 14% (16/115) in the CRT arm versus 36% (40/114) in the SBRT arm (P < .001) achieved a CR to pain. This significance was retained in multivariable analyses (P < .001) and the risk ratio (RR) was 1.33 (95% CI, 1.14-1.55) favoring SBRT.

At 6 months, 16% (18/115) in the CRT arm versus 33% (37/114) in the SBRT arm achieved a CR (P = .004), with significance again retained on multivariate analysis (P < .001); additionally, the RR was 1.24 (95% CI, 1.07-1.44) favoring SBRT.

“This was not just, ‘Oh, I feel a little bit better,’” said Sahgal, adding that patients experienced the reduction in pain without increasing the use of pain medications.

“We applied a very stringent trial design to focus on the impact of radiation,” Sahgal continued. “It was the radiation treatment that led to the improvement.”

There was no difference between the study arms in RSS PFS or overall survival (OS). The 3-month RSS PFS for CRT versus SBRT was 86% versus 92% (P = .4), and at 6 months was 69% versus 75% (P = .42), respectively. For QoL outcomes, only financial perception at 1 month significantly differed (P = .03) and favored SBRT.

Regarding safety, both treatments were found to be safe with respect to fractures and there was no radiation damage to the spinal cord observed in either cohort. There were 20 (17%) patients in the CRT arm and 12 (11%) in the SBRT arm with post-radiation vertebral compression fractures. Further, 2 (2%) patients in the CRT am and none (0%) in the SBRT arm progressed to malignant epidural spinal cord compression.

Grade 2 or more adverse events (AEs) were seen in 12% and 11% in the CRT and SBRT arms, respectively, and no Grade 5 AEs were observed.

“We saw we were getting improvements in pain, but our patients were not pain-free. With the development of SBRT, and spinal SBRT in particular, we started to wonder if we could do better. With these new research results, we think we can,” Sahgal concluded.

References:

1. Sahgal A, Myrehaug SD, Siva S, et al. CCTG SC.24/TROG 17.06: A Randomized Phase II/III Study Comparing 24Gy in 2 Stereotactic Body Radiotherapy (SBRT) Fractions Versus 20Gy in 5 Conventional Palliative Radiotherapy (CRT) Fractions for Patients with Painful Spinal Metastases. Presented at the American Society for Radiation Oncology (ASTRO) Annual Meeting. Abstract #: LBA 2.

2. Treating spinal metastases with fewer and higher doses of radiation reduces pain more effectively [news release]. Arlington, Virginia. Published October 26, 2020. Accessed October 30, 2020. https://www.newswise.com/articles/treating-spinal-metastases-with-fewer-and-higher-doses-of-radiation-reduces-pain-more-effectively?sc=sphr&xy=10021790