Consensus Contouring Guidelines for Post-Operative Completely Resected Cavity Stereotactic Radiosurgery (SRS) for Brain Metastases

Publication date: Available online 4 October 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Hany Soliman, Mark Ruschin, Lilyana Angelov, Paul D. Brown, Veronica L.S. Chiang, John P. Kirkpatrick, Simon S. Lo, Anita Mahajan, Kevin S. Oh, Jason P. Sheehan, Scott G. Soltys, Arjun Sahgal
PurposeCavity stereotactic radiosurgery (SRS) is an emerging treatment option after surgical resection of brain metastases. No guidelines for contouring the surgical cavity volume have been reported. The aim of this study was to propose contouring guidelines based on consensus contours generated by 10 international experts.MethodsTen post-operative completely resected cases with varying clinical scenarios and locations within the brain were selected. For each case, 10 experts independently contoured the surgical cavity clinical target volume (CTV). All the contours were analyzed and agreement was calculated using the Simultaneous Truth and Performance Level Estimation (STAPLE) with the kappa statistic. A follow-up survey was also completed by each investigator in order to summarize their contouring rationale based on a number of different clinical scenarios. Both the results from the survey and consensus STAPLE contours were summarized to establish contouring guidelines.ResultsThere was a high level of agreement between the expert CTV contours (mean sensitivity=0.75, mean specificity=0.98), and the mean kappa was 0.65. The agreement was statistically significant at p<0.001 for all cases. Based on these results and analyses of the survey answers, recommendations for CTV include: fusion of the pre-operative MRI to aid in volume delineation, contouring the entire surgical tract regardless of the preoperative location of the tumor, the CTV should be extended 5-10mm along the dura overlying the bone flap to account for microscopic disease extension in cases with preoperative dural contact, and a margin of up to 5mm into the adjacent sinus is sufficient when there is pre-operative venous sinus contact.ConclusionsConsensus contouring guidelines for post-operative completely resected cavity SRS treatment were established based on expert contours and clinical practice. However, in the absence of clinical data supporting the recommendations in this paper, these guidelines serve as a baseline for further study and refinement.



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