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The volumetric response of brain metastases after stereotactic radiosurgery and its post-treatment implications
Suzanne R Sharpton1, Eric K Oermann, Dominic T Moore
1*Department of Internal Medicine, University of California San Francisco, San Francisco, California; ‡Department of Neurological Surgery, University of North Carolina School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North California; §Department of Biostatistics, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, North California; ¶Radiation Oncology, University of North Carolina School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North California.
Background:
Changes in tumor volume are seen on magnetic resonance imaging within weeks after stereotactic radiosurgery (SRS), but it remains unclear what clinical outcomes early radiological changes portend.
Objective:
We hypothesized that rapid, early reduction in tumor volume post-SRS is associated with prolonged local control and favorable clinical outcome.
Methods:
A retrospective review of patients treated with CyberKnife SRS for brain metastases at the University of North Carolina from 2007 to 2009 was performed. Patients with at least 1 radiological follow-up, minimal initial tumor volume of 0.1 cm, no previous focal radiation, and no recent whole-brain radiation therapy were eligible for inclusion.
Results:
Fifty-two patients with 100 metastatic brain lesions were analyzed and had a median follow-up of 15.6 months (range, 2-33 months) and a median of 2 (range, 1-8) metastatic lesions. In treated metastases in which there was a significant tumor volume reduction by 6 or 12 weeks post-SRS, there was no local progression for the duration of the study. Furthermore, patients with metastases that did not reduce in volume by 6 or 12 weeks post-SRS were more likely to require corticosteroids (P = .01) and to experience progression of neurological symptoms (P = .003).
Conclusion:
Significant volume reductions of brain metastases measured at either 6 or 12 weeks post-SRS were strongly associated with prolonged local control. Furthermore, early volume reduction was associated with less corticosteroid use and stable neurological symptoms.
