Influence of Radiosurgery Dose on Pain Relief for Spinal Metastasis

Abstract

Bone pain from spinal metastatic disease is an important influencer on quality of life in patients with metastatic disease. With advancements in treatment delivery techniques, stereotactic radiosurgery (SRS) is an emerging treatment approach for localized spinal metastases, though the optimal dose remains unclear. We evaluated pain response in patients with spinal metastases who were treated with SRS to determine if dose was a predictor of effective treatment. This was a study of patients from a prospective SRS Registry. Eligible patients received SRS for bone pain, had recorded pain scores before and after treatment, and had adequate follow-up to evaluate pain response. Radiation details including dose and fractionation were collected and converted to a biologically effective dose (BED) using an alpha/beta of 10. An effective treatment was defined as improvement in pain without pain recurrence or radiographic progression of the treated bone metastatic lesion. Ninety-seven patients met the eligibility criteria, with a median follow-up of 8.5 months. The median dose prescribed was 24 Gy (range 6 Gy- 35 Gy) and the median number of fractions used was 3 (range 3-5). The median BED was 41.6 Gy (range 15.7 Gy – 60 Gy). Effective treatment was achieved in 84 patients (86.6%). Seven patients (7.2%) with an initial pain response had either pain recurrence in the treated area or radiographic progression. Six patients (6.2%) did not have pain improvement. Thus, 13 treatments (13.4%) were considered ineffective. The mean BED for ineffective treatments was 35.3 Gy versus 42.0 Gy for effective treatment (p = .025). We found that effective SRS treatments were associated with higher BED. Although emerging randomized data (RTOG 0631) failed to demonstrate a difference in 3-month pain response between SRS and conventionally fractionated external beam radiotherapy, a higher dose on the SRS arm may have improved this outcome.