Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
Presenter(s)
Mitchell Parker, MD, PhD - Memorial Sloan Kettering Cancer Center, New York, NY
M. I. Parker1, D. T. Bergman1, A. Ballangrud2, A. J. Abaya1, L. Kuo2, M. Aristophanous2, N. Leclair1, M. Zinovoy1, A. R. Barsky1, J. Y. Shin1, A. J. Khan1, Y. Yamada1, B. S. Imber3, C. Kinslow1, C. B. Jackson1, G. Cederquist1, D. Yerramilli1, Z. R. Moore1, D. Billing1, Y. Yu1, and L. R. G. Pike1,3; 1Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 2Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, 3Memorial Sloan Kettering Cancer Center, New York, NY
Purpose/Objective(s):
WBRT causes neurocognitive decline, and avoiding it is a goal of modern brain metastasis (BM) management. Stereotactic radiosurgery/therapy (SRS/SRT) preserves cognition while achieving equivalent survival, yet its use has largely been limited to patients with few lesions, leaving those with high intracranial burden defaulting to WBRT by convention rather than evidence. LINAC-based SRS/SRT enables rapid treatment of numerous lesions per isocenter with reduced integral brain dose, yet data supporting SRS/SRT over WBRT at high lesion counts remain limited. Here we report overall survival (OS) and salvage patterns across the full spectrum of intracranial disease burden in the largest contemporary linac-based SRS/SRT registry.Materials/Methods:
We retrospectively analyzed patients treated with SRS/SRT (1–5 fractions) between 2017–2025 at any of 7 sites within a single NCI-designated comprehensive cancer center. Treated lesion number at first course was categorized as 1, 2–4, 5–10, 11–20, and >20. OS was measured from first course. Multivariable Cox regression adjusted for demographics, histology, and prior WBRT/craniotomy. Competing-risk analyses (death as competing event) estimated cumulative incidence of repeat SRS/SRT, salvage WBRT, and craniotomy.Results:
3,965 patients were treated across 6,040 courses encompassing 20,260 targets. Median age was 65 years and median follow-up 38.8 months. Histologies included NSCLC (26.8%), breast (15.3%), GI (9.0%), and melanoma (6.1%). Prior WBRT and craniotomy were present in 3.0% and 18.9% of patients, respectively. OS declined with lesion burden but plateaued at =5 lesions: median OS was 16.5 mo for single-lesion patients (n=1,758, ref), 10.7 mo for 2–4 lesions (n=1,349; HR 1.38, 95% CI 1.26–1.50), 8.0 mo for 5–10 (n=631; HR 1.64, 95% CI 1.48–1.83), 7.5 mo for 11–20 (n=192; HR 1.80, 95% CI 1.49–2.16), and 5.8 mo for >20 lesions (n=35; HR 2.49, 95% CI 1.63–3.80; all p<1×10?5). Repeat SRS was more frequent with 2–4 (HR 1.61, 95% CI 1.41–1.84), 5–10 (HR 1.79, 95% CI 1.51–2.12), and 11–20 lesions (HR 2.32, 95% CI 1.76–3.05; all p<1×10?5) but not >20 lesions (HR 2.02, 95% CI 0.96–4.27; p=0.07). Critically, salvage WBRT and craniotomy remained rare: among >1 versus 1-lesion patients, 12-month salvage WBRT was statistically but not clinically significantly higher at 4.8% vs 2.7% (HR 1.40, p=0.02), and craniotomy 3.7% vs 4.2% (HR 0.83, p=0.12).Conclusion:
OS declined with lesion burden but plateaued at =5 metastases. WBRT was deferred in most patients regardless of lesion count. In the modern era of effective systemic therapies that control micrometastatic intracranial disease and improve extracranial disease control, patients with a large number of BM should be offered upfront SRS/SRT, as they stand to gain the most from avoiding the long-term cognitive consequences of WBRT. These data strongly support an SRS/SRT-first strategy even for high-volume intracranial disease.