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Vienna, Austria

ESTRO 2023

Session Item

CNS
Poster (Digital)
Clinical
Mimicking neoadjuvant stereotactic radiosurgery for resection cavities of brain metastases
Carolin Senger, Germany
PO-1119

Abstract

Mimicking neoadjuvant stereotactic radiosurgery for resection cavities of brain metastases
Authors:

Carolin Senger1, Marcel Nachbar1, Nina Soffried2, Bohdan Bodnar2, Anastasia Janas3, Goda Kalinauskaite4, Anne Kluge5, David Schultz6, Alfredo Conti7, David Kaul8,9, Daniel Zips5, Peter Vajkoczy10, Gueliz Acker11,10,12

1Charité - Universitätsmedizin Berlin , Department of Radiation Oncology and Radiotherapy, Berlin, Germany; 2Charité - Universitätsmedizin Berlin , Department of Radiation Oncology and Radiotherapy, Berlin , Germany; 3Charité - Universitätsmedizin Berlin , Department of Neurosurgery, Berlin, Germany; 4Charité - Berlin Universitätsmedizin, Department of Radiation Oncology and Radiotherapy, Berlin , Germany; 5Charité - Universitätsmedizin Berlin, Department of Radiation Oncology and Radiotherapy, Berlin, Germany; 6University of Toronto, Department of Radiation Oncology, Toronto, Canada; 7Alma Mater Studiorum - Università di Bologna, Department of Biomedical and Neuromotor Sciences, Bologna, Italy; 8Charité - Universitätsmedizin Berlin, Department of Radiation Oncology and Radiotherapy, Belrin, Germany; 9German Cancer Consortium (DKTK), German Cancer Research Center (DKFZ), Heidelberg, Germany; 10Charité - Universitätsmedizin Berlin, Department of Neurosurgery, Berlin, Germany; 11Charité - Universitätsmedizin Berlin , Radiation Oncology and Radiotherapy, Berlin, Germany; 12Berlin Institute of Health, Clinician Scientist Program, Berlin, Germany

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Purpose or Objective

Neoadjuvant stereotactic radiosurgery (Na-SRS) of brain metastases has gained importance, but it is not routinely performed. While awaiting the results of prospective studies, we aimed to analyze the changes in the volume of brain metastases irradiated pre- and postoperatively and the resulting dosimetric effects on normal-brain-tissue (NBT).

Material and Methods

We identified patients treated with SRS at our institution to compare hypothetical preoperative gross tumor and planning-target-volumes (preGTV and prePTV) with original postoperative resection cavity volumes (postGTV and postPTV) as well as with a standardized-hypothetical PTV with 2.0 mm margin (Wilcoxon test). We used Pearson-correlation to assess the association between the GTV and PTV changes with the preGTV. A multiple linear regression analysis was established to predict the GTV-change. The hypothetical planning for the selected cases to assess the volume effect showed NBT exposure with a median of only 67.6% (range: 33.2%-84.5%) of postPTV receiving the fractionation-specific evaluated dose. We performed a literature review on Na-SRS and searched for ongoing prospective trials.

Results

We included 30 patients in the analysis. The pre/postGTV and pre/postPTV did not differ significantly. We observed a negative correlation between preGTV and GTV-change, which was also a predictor of volume change in the regression analysis, in terms of a larger volume change for a smaller pre-GTV. In total, 62.5% of cases with an enlargement of >5.0 cm3 were smaller tumors (preGTV<15.0 cm3), whereas larger tumors (>25.0 cm3) showed only a decrease in postGTV. The hypothetical planning for the selected cases to assess the volume effect showed NBT exposure with a median of only about 67.6% (range: 33.2%-84.5%) of postPTV receiving the fractionation-specific evaluated dose. Nine published studies and twenty ongoing studies are listed as an overview.



Conclusion

Patients with smaller brain metastases may have a higher risk of volume increase when irradiated postoperatively. Target volume delineation is of great importance because the PTV directly affects the exposure of NBT, but it is a challenge when contouring resection cavities. Further studies should identify patients at risk of relevant volume increase to be preferably treated with Na-SRS in routine practice. Ongoing clinical trials will evaluate additional benefits of Na-SRS.