The volumetric response of brain metastases after stereotactic radiosurgery and its post-treatment implications.
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).


CONCLUSIONS
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.
*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.
Suzanne R
SR
Sharpton
Eric K
EK
Oermann
Dominic T
DT
Moore
Eric
E
Schreiber
Riane
R
Hoffman
David E
DE
Morris
Matthew G
MG
Ewend
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000473:pathology / Q000601:surgery; D001932:Brain Neoplasms / Q000556:secondary* / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery; D012189:Retrospective Studies; D016896:Treatment Outcome