Outcomes and Toxicity of Single- And Multi-Fraction Spine Radiosurgery for Three or More Vertebral Bodies

Abstract

Spine radiosurgery is an accepted standard treatment for vertebral body metastases and is traditionally restricted to one or two consecutive vertebral bodies due to toxicity concerns with larger volumes. Thus, the outcomes and toxicity of radiosurgery to a larger volume of three or more vertebral bodies are poorly characterized. We sought to describe our single-institution experience of treating patients with radiosurgery to three or more consecutive vertebral bodies. An IRB-approved retrospective review of our prospectively maintained radiosurgery database was performed. Inclusion criteria were men and women receiving single- or multi-fraction spine radiosurgery to three or more consecutive vertebral bodies with at least one month of follow-up. We recorded outcome data such as local control, overall survival, and pain response. Local progression was defined as radiologic progression, recurrent pain in the treatment field, or a vertebral body metastasis in the body adjacent to the treatment volume. Pain scores (scored 0-10) in the treated area were evaluated within one month before treatment and in longer follow-up. Average change in pain score after treatment was reported. Karnofsky performance status (KPS) was also evaluated within one month before treatment and in follow up. KPS was based on debilitation from tumors at the treated site. Toxicity endpoints of interest were radiation myelopathy and vertebral body fracture. 32 patients were identified (18 male, 14 female), and 35 total sites were treated. Median age of patient at time of SRS treatment was 59. Median dose in single fraction was 1300cGy (range: 800-1800cGy), and median dose in multiple fractions was 2400cGy (range: 1800-3000cGy). 21% of patients had cervical spine metastases, 55% with thoracic spine metastases, and 24% with lumbar spine metastases, with primary tumor sites including colon, breast, thymus, pelvis, lung, mammary gland, kidney, thyroid, nasopharynx, rhabdomyosarcoma, bone, schwannoma, and vulva. 14/32 (43%) patients had epidural or paraspinal soft tissue components of their disease. The six-month local control rate was 77%. The one-year survival rate was 49%. Average change in pain score was -.5 (range: -7-+4, st dev ±2.55). Median pre-treatment KPS was 90%, and median post-treatment KPS was 80%, with 7/32 (22%) patients having a decline in 20% or greater, and 2/32 (6.2%) patient having an improvement of 20% or greater. Incidence of vertebral compression fracture was 4/32 (12.5%), and radiation myelopathy was 0/32 (0%). Treatment of patients with radiosurgery to three or more consecutive vertebral body metastases is well tolerated. For the majority of treated patients, single- or multi-fraction radiosurgery provides durable local control, modest pain relief, preserved quality of life, and low rates of severe toxicity.