Patterns of Failure After Stereotactic Body Radiotherapy to Sacral Metastases

R Ratnakumaran; N van As; V Khoo; F McDonald; D Tait; M Ahmed; H Taylor; C Griffin; E M Dunne; A C Tree

doi:10.1016/j.clon.2023.01.020

Patterns of Failure After Stereotactic Body Radiotherapy to Sacral Metastases

Clin Oncol (R Coll Radiol). 2023 May;35(5):339-346. doi: 10.1016/j.clon.2023.01.020. Epub 2023 Feb 3.

Authors

R Ratnakumaran¹, N van As², V Khoo², F McDonald², D Tait², M Ahmed², H Taylor³, C Griffin⁴, E M Dunne⁵, A C Tree²

Affiliations

¹ The Royal Marsden NHS Foundation Trust, Sutton, UK; Radiotherapy and Imaging Division, Institute of Cancer Research, London, UK. Electronic address: ragu.ratnakumaran@icr.ac.uk.
² The Royal Marsden NHS Foundation Trust, Sutton, UK; Radiotherapy and Imaging Division, Institute of Cancer Research, London, UK.
³ The Royal Marsden NHS Foundation Trust, Sutton, UK.
⁴ The Institute of Cancer Research, Clinical Trials and Statistics Unit, London, UK.
⁵ Department of Radiation Oncology, BC Cancer - Vancouver Centre, Vancouver, British Columbia, Canada.

PMID: 36805131
DOI: 10.1016/j.clon.2023.01.020

Abstract

Aims: Stereotactic body radiotherapy (SBRT) is increasingly used to treat sacral metastases. We analysed our centre's local relapse rates and patterns of failure after sacral SBRT and assessed whether using the consensus contouring recommendation (CCR) may have prevented local relapse.

Materials and methods: We conducted a single-centre retrospective review of patients treated with sacral SBRT between February 2012 and December 2021. The cumulative incidence of local relapse, patterns of failure and overall survival were determined. Two investigators reviewed planning computed tomography scans and imaging at relapse to determine if local relapse was potentially preventable with a larger CCR-derived radiotherapy field.

Results: In total, 34 patients received sacral SBRT, with doses ranging from 24 to 40 Gy over three to five fractions. The most frequently used schedule was 30 Gy in three fractions. Common primaries treated included prostate (n = 16), breast (n = 6), lung (n = 3) and renal (n = 3) cancers. The median follow-up was 20 months (interquartile range 13-55 months). The cumulative incidence of local relapse (4/34) was 2.9% (95% confidence interval 0.2-13.2), 6.3% (95% confidence interval 1.1-18.5) and 16.8% (95% confidence interval 4.7-35.4) at 6 months, 1 year and 2 years, respectively. The patterns of failure were local-only (1/34), local and distant (3/34) and distant relapse (10/34). The overall survival was 96.7% (95% confidence interval 90.5-100) and 90.6% (95% confidence interval 78.6-100) at 1 and 2 years, respectively. For prostate/breast primaries, the cumulative incidence of local relapse was 4.5% (95% confidence interval 0.3-19.4), 4.5% (95% confidence interval 0.3-19.4) and 12.5% (95% confidence interval 1.7-34.8) at 6 months, 1 and 2 years, respectively. Twenty-nine cases (85.3%) deviated from the CCR. Sacral relapse was potentially preventable if the CCR was used in one patient (2.9% of the whole cohort and 25% of the relapsed cohort).

Discussion: We have shown excellent local control rates with sacral SBRT, which was largely planned with a margin expansion approach.

Keywords: Local control; oligometastases; patterns of failure; sacrum; stereotactic body radiotherapy.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Humans
Male
Neoplasms* / pathology
Radiosurgery* / methods
Recurrence
Retrospective Studies
Sacrum / surgery