Main Session
Sep
29
PQA 03 - Central Nervous System, Professional Development/Medical Education
2554 - Clinical Target Volume Delineation in Stereotactic Radiosurgery for Sacral Spine Metastases
Presenter(s)
Joseph Abi Jaoude, MD - Stanford University, Stanford, CA
J. Abi Jaoude1, D. Klebaner2, T. L. Kaneko2, R. M. R. Laljani3, A. Pratapneni2, T. Kollipara4, E. Rahimy2, I. C. Gibbs2, S. D. Chang5, D. Park5, E. L. Pollom2, and S. G. Soltys2; 1Stanford University School of Medicine, Stanford, CA, 2Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, 3Stanford University, Stanford, CA, 4Department of Radiation Oncology, Stanford University, Palo Alto, CA, 5Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA
Purpose/Objective(s):
For patients with sacral spine metastases treated with stereotactic radiosurgery (SRS), minimal data exist to guide clinical target volume (CTV) delineation. We present our preliminary experience with sacral spine SRS using various CTV delineation methods.Materials/Methods:
We retrospectively reviewed patients treated at our institution with sacral spine SRS. Treatment volumes were categorized into 3 groups by how the CTV was contoured: 1) CTV=GTV (gross tumor volume), 2) CTV=GTV plus additional margin, and 3) CTV delineated based on the international consensus recommendations for sacral spine SRS. We analyzed differences in cumulative incidence of local failure (LF) at 1- and 2-years following SRS, with death as competing risk, between different CTV delineation methods.Results:
In total, 42 patients with 59 sacral spine metastases treated with SRS were included in our study. 19 tumors (32%) were treated with CTV=GTV, 29 (49%) with additional CTV margin, and 11 (19%) with consensus guidelines. For tumors treated with CTV margin, the median margin used was 5mm (IQR 3-6mm). The median dose and fractions for tumors treated with CTV=GTV, CTV margin, and consensus guidelines were 24Gy/3fx, 20Gy/1fx, and 30Gy/4fx, and the median single fraction equivalent dose (SFED) was 17Gy, 19Gy, and 18Gy, respectively. Median follow up time following SRS was 6.7 months. The 1- and 2-year cumulative incidences of LF was 24%/24% for CTV=GTV, 14%/14% for CTV margin, and 0/10% for consensus guidelines, respectively (P=0.6). In-field LF occurred in 0/4 (0%) of tumors treated with CTV=GTV, 4/5 (80%) of tumors treated with CTV margin, and 0/1 (0%) of tumors treated with consensus guidelines.Conclusion:
The addition of a CTV margin around the GTV for sacral spine SRS appears numerically better than the addition of no margin. The interaction and impact on local control between higher dose to smaller target volumes versus lower dose to larger target volumes will be further explored pending data collection for our entire patient cohort.