Central Nervous System

PD 03 - CNS 1 - Poster Discussion - Toxicity and Quality of Life

1026 - Adverse Radiation Effect following Repeat Stereotactic Radiosurgery for Brain Metastases

Sunday, October 21
5:33 PM - 5:39 PM
Location: Room 217 A/B

Adverse Radiation Effect following Repeat Stereotactic Radiosurgery for Brain Metastases
J. Chan1, S. E. Braunstein2, J. L. Nakamura3, S. E. Fogh2, L. Ma3, D. Raleigh3, P. L. Menzel3, E. B. Golden3, P. V. Theodosopoulos4, M. W. McDermott4, and P. K. Sneed2; 1University of California San Francisco, Department of Radiation Oncology, San Francisco, CA, 2University of California, San Francisco, San Francisco, CA, 3University of California, San Francisco, Department of Radiation Oncology, San Francisco, CA, 4University of California San Francisco, Department of Neurological Surgery, San Francisco, CA

Purpose/Objective(s): We previously published a rigorous analysis of both overall and symptomatic adverse radiation effect (ARE) in more than 2000 brain metastases treated with stereotactic radiosurgery (SRS), excluding lesions treated with repeat SRS. Here we evaluate actuarial probabilities and risk factors of ARE after repeat SRS to same lesions, which is an increasingly common scenario in long-term survivors of brain metastases.

Materials/Methods: Recurrent brain metastases treated with repeat single-fraction SRS from September 1998 through December 2016 at a single institution were analyzed. Prescription doses were reduced by 0-1 Gy to take into account prior SRS. Follow-up MR imaging and salvage surgery operative and pathology reports after repeat SRS were used to score local failure (LF) and ARE. Cumulative incidence of LF and ARE were estimated with censoring at the date of last imaging follow-up. Overall survival was estimated with the Kaplan-Meier method from the date of repeat SRS. Multivariate analysis was performed using Cox proportional hazards regression.

Results: Among a total of 9475 brain metastases treated in 1581 patients with fixed-frame SRS, a subset of 267 lesions in 132 patients (40% breast, 29% lung, 16% melanoma, 5% GI, 10% other) were treated with repeat single-fraction SRS to the same lesion. The median survival of this highly selected cohort was 17.4 months after repeat SRS (IQR 10.1-29.4 mo). The median interval between SRS sessions for individual lesions was 13.8 months (IQR 7.0-22.8 mo). Ultimately, 209 retreated lesions in 111 patients were evaluable for LF and ARE scoring after excluding 50 lesions in 19 patients without imaging follow-up, 7 lesions in 2 patients for whom outcome scoring became confounded by a large number of new brain metastases, and one lesion resected prior to repeat SRS. Among these 209 evaluable metastases, the median quadratic mean diameter (QMD) was 1.2 cm (range, 0.2-4.4 cm), prescribed dose 18 Gy (range, 12-20 Gy), and imaging follow-up 13.2 months (IQR, 5.3-29.2 months). The actuarial probabilities of LF were 6% at 6 months and 17% at 12 months. The probabilities of imaging ARE and symptomatic ARE were 10% and 5% at 6 months and 34% and 16% at 12 months. A large proportion of lesions with symptomatic ARE (67%) did not improve radiographically with medical therapy. Higher risk of symptomatic ARE was associated with QMD≥ 1 cm (p = 0.031). Short interval of <6 months (p < 0.001) to repeat SRS and QMD ≥ 2 cm (p = 0.001) were risk factors for LF.

Conclusion: Repeat SRS for brain metastases < 2 cm yields good local control with acceptable risk of symptomatic ARE. We recommend repeat SRS dose of at least 18 Gy. Surgery or fractionated treatment should be considered for salvage treatment of brain metastases ≥ 2 cm.

Author Disclosure: J. Chan: None. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC. J.L. Nakamura: None. S.E. Fogh: None. L. Ma: Patent/License Fees/Copyright; University of California Regents. D. Raleigh: None. P.L. Menzel: None. P.V. Theodosopoulos: None. M.W. McDermott: None. P.K. Sneed: Honoraria; CareCore National, LLC. Travel Expenses; CareCore National, LLC. Board Member; North American Gamma Knife Consortium.

Jason Chan, MD

UCSF Radiation Oncology

Disclosure:
No relationships to disclose.

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