Magnetic Resonance Imaging Frequency After Stereotactic Body Radiation Therapy for Spine Metastases

Hanbo Chen; Eshetu G Atenafu; K Liang Zeng; Aimee Chan; Jay Detsky; Sten Myrehaug; Hany Soliman; Chia-Lin Tseng; Arjun Sahgal; Pejman J Maralani

doi:10.1016/j.ijrobp.2024.02.010

Magnetic Resonance Imaging Frequency After Stereotactic Body Radiation Therapy for Spine Metastases

Int J Radiat Oncol Biol Phys. 2024 Feb 17:S0360-3016(24)00319-5. doi: 10.1016/j.ijrobp.2024.02.010. Online ahead of print.

Authors

Affiliations

¹ Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada. Electronic address: hanbo.chen@sunnybrook.ca.
² Department of Biostatistics, University Health Network, University of Toronto, Toronto, Ontario Canada.
³ Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, Toronto, Ontario, Canada.
⁴ Department of Medical Imaging, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.

PMID: 38373656
DOI: 10.1016/j.ijrobp.2024.02.010

Abstract

Purpose: Stereotactic body radiation therapy (SBRT) is increasingly being used to treat spine metastases. Current post-SBRT imaging surveillance strategies in this patient population may benefit from a more data-driven and personalized approach. The objective of this study was to develop risk-stratified post-SBRT magnetic resonance imaging (MRI) surveillance strategies using quantitative methods.

Methods and materials: Adult patients with bony spine metastases treated with SBRT between 2008 and 2021 and who had at least 2 follow-up spine MRIs were reviewed retrospectively. A recursive partitioning analysis model was developed to separate patients into different risk categories for post-SBRT progression anywhere within the spine. Imaging intervals were derived for each risk category using parametric survival regression based on multiple expected spine progression rates per scan.

Results: A total of 446 patients and 1039 vertebral segments were included. Cumulative incidence of spine progression was 19.2% at 1 year, 26.7% at 2 years, and 35.3% at 4 years. The internally validated risk stratification model was able to divide patients into 3 risk categories based on epidural disease, paraspinal disease, and Spinal Instability Neoplastic Score category. The 4-year risk of spine progression was 23.4%, 39.0%, and 51.8%, respectively, for the low-, intermediate-, and high-risk groups. Using an expected per-scan spine progression rate of 3.75%, the low-risk group would require follow-up scans every 6.0 months (95% CI, 4.9-7.6) and the intermediate-risk group would require surveillance every 3.1 months (95% CI, 2.6-3.7). At an expected spine progression rate of 5%, the high-risk group would require surveillance every 1.3 months (95% CI, 1.1-1.6) during the first 13.2 months after SBRT and every 5.9 months thereafter (95% CI, 2.8-12.3).

Conclusions: Data-driven follow-up MRI surveillance intervals at a range of expected spine progression rates have been determined for patients at different risks of spine progression based on an internally validated, single-institution risk stratification model.