Abstract
The purpose of this critical review is to summarize the literature specific to single-fraction stereotactic radiosurgery (SRS) and multiple-fraction stereotactic radiation therapy (SRT) for postoperative brain metastases resection cavities and to present practice recommendations on behalf of the ISRS. The Medline and Embase databases were used to apply the Preferred Reporting Items for Systematic Reviews and Meta-Analyses approach to search for manuscripts reporting SRS/SRT outcomes for postoperative brain metastases tumor bed resection cavities with a search end date of July 20, 2018. Prospective studies, consensus guidelines, and retrospective series that included exclusively postoperative brain metastases and had at minimum 100 patients were considered eligible. The Embase search revealed 157 manuscripts, of which 77 were selected for full-text screening. PubMed yielded 55 manuscripts, of which 23 were selected for full text screening. We deemed 8 retrospective series, 1 phase 2 prospective study, 3 randomized controlled trials, and 1 consensus contouring paper appropriate for inclusion. The data suggest that SRS/SRT to surgical cavities with prescription doses of 30 to 50 Gy equivalent effective dose (EQD) 210, 50 to 70 Gy EQD25, and 70 to 90 EQD22 are associated with rates of local control ranging from 60.5% to 91% (median, 80.5%). Randomized data suggest improved local control with single-fraction SRS compared with observation and improved cognitive outcomes compared with whole-brain radiation therapy (WBRT). The toxicity of SRS/SRT in the postoperative setting was limited and is reviewed herein. Although randomized data raise concern for poorer local control after resection cavity SRS than WBRT, these findings may be driven by factors such as conservative prescription doses used in the SRS arm. Retrospective studies suggest high rates of local control after single-fraction SRS and hypofractionated SRT for postoperative brain metastases. With a superior neurocognitive profile and no survival disadvantage to withholding WBRT, the ISRS recommends SRS as first-line treatment for eligible postoperative patients. Emerging data suggest that fractionated SRT may provide superior local control compared with single-fraction SRS, in particular, for large tumor cavity volumes/diameters and potentially for patients with a preoperative diameter greater than 2.5 cm.
Highlights
The first landmark study by Patchell et al,[1] reported in 1990, randomized patients with a solitary brain metastasis to wholebrain radiation therapy (WBRT) alone versus surgery followed by WBRT
Retrospective series with
The prescription doses used in this study are variable but, in aggregate, suggest that prescriptions ranging from 30 to 50 Gy EQD210, 50 to 70 EQD25, and 70 to 90 EQD22 are associated with satisfactory outcomes
Summary
The first landmark study by Patchell et al,[1] reported in 1990, randomized patients with a solitary brain metastasis to wholebrain radiation therapy (WBRT) alone versus surgery followed by WBRT. They reported significant improvements in both local control (LC) and overall survival in patients who underwent surgery. The second landmark study by Patchell et al,[2] reported in 1998, randomized patients after surgery to observation versus adjuvant WBRT, and significant benefits were reported with respect to LC. The standard of care had been adjuvant WBRT based on the discussed historic randomized trials, but recently this has been challenged with the application of SRS and SRT to the surgical bed. Early adopters began treating surgical cavities with either a single-fraction SRS or up to 5 fractions of SRT, it was not until 2018 that dedicated randomized trials were reported
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