Program Information
Does Size Matter? Investigating the Optimal Planning Target Volume Margin for Post-Operative Stereotactic Radiosurgery Alone to Resected Brain Metastases
J Jhaveri1*, X Zhang2 , M Chowdhary3 , J Switchenko4 , R Press5 , R Cassidy6 , T Morgan7 , J Roper8 , A Dhabaan9 , E Elder10 , J Olson11 , B Eaton12 , W Curran13 , H Shu14 , I Crocker15 , K Patel16 , (1) Emory University, Atlanta, GA(2) Emory University, Atlanta, Georgia, (3) Rush University, Chicago, Illinois, (4) Emory University, Atlanta, GA, (5) Emory University, Atlanta, GA, (6) Emory University, Atlanta, GA, (7) Emory University, Atlanta, GA, (8) Winship Cancer Institute of Emory University, Atlanta, Georgia, (9) Winship Cancer Institute of Emory University, Atlanta, GA, (10) Emory University, Winship Cancer Institute, Atlanta, Georgia, (11) Emory University, Atlanta, GA, (12) Emory University, Atlanta, GA, (13) Emory University, Atlanta, GA, (14) Emory University, Atlanta, GA, (15) Emory University, Atlanta, GA, (16) Emory University, Atlanta, GA
Presentations
SU-I-GPD-T-626 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: The aim of this study is to compare the effect of PTV margin size on local recurrence (LR) and symptomatic radiation necrosis (SRN) for resected brain metastases (BM) treated with Stereotactic Radiosurgery(SRS).
Methods: A total of 133 consecutive BM patients with 141 resection cavities treated with LINAC based SRS alone from 2005-2016 were retrospectively identified. Patients were stratified into two groups: PTV margin size = 1.0 mm and > 1.0 mm. Kaplan Meier and cumulative incidence models were utilized to estimate overall survival and intracranial outcomes, respectively. Multivariable analyses (MVA) were also performed.
Results: There were 36 patients (27.1%) with 37 lesions in the 1mm margin group while 97 patients (72.9%) with 104 lesions had a margin >1.0mm to 3.0mm (median 2.0mm). Patient baseline and dosimetric characteristics were balanced between groups, except for patients treated in the 1mm margin cohort were more likely to have ECOG (Eastern Cooperative Oncology Group) performance status 0 (36.1% vs. 19.6%) and treated with framed technique (92% vs. 66%), both p<0.05. The median cavity size was not statistically different between the two groups: 10.4 vs. 11.9 cm3 (p=0.285). Median survival and follow-up for all patients was 15.6 months and 17.7 months, respectively. The 1-year LR rate was 14.3% for both groups (p=0.979). MVA demonstrated margin size was not a predictor for LR. The larger margin group was associated with higher 1-year rate of SRN: 20.9% vs. 6.0% (p=0.025). On MVA, larger margin size demonstrated a trend towards increased risk of SRN: Hazard Ratio 3.12, 95% confidence interval: 0.97-10.02 (p=0.056).
Conclusion: For SRS to resected BM, expanding the PTV margin beyond 1 mm is not associated with an improvement in LR but appears to increase risk of SRN. Further prospective analyses to identify the optimal margin are warranted.
Contact Email: