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PT  - JOURNAL ARTICLE
AU  - Patel, T.R.
AU  - McHugh, B.J.
AU  - Bi, W.L.
AU  - Minja, F.J.
AU  - Knisely, J.P.S.
AU  - Chiang, V.L.
TI  - A Comprehensive Review of MR Imaging Changes following Radiosurgery to 500 Brain Metastases
AID  - 10.3174/ajnr.A2668
DP  - 2011 Nov 01
TA  - American Journal of Neuroradiology
PG  - 1885--1892
VI  - 32
IP  - 10
4099  - http://www.ajnr.org/content/32/10/1885.short
4100  - http://www.ajnr.org/content/32/10/1885.full
SO  - Am. J. Neuroradiol.2011 Nov 01; 32
AB  - BACKGROUND AND PURPOSE: Stereotactic radiosurgery is known to control 85%–95% of intracranial metastatic lesions during a median survival of 6–8 months. However, with the advent of newer systemic cancer therapies, survival is improving; this change mandates a longitudinal quantitative analysis of the radiographic response of brain metastases to radiosurgery. MATERIALS AND METHODS: MR imaging of 516 metastases in 120 patients treated with GK-SRS from June 2006 to December 2009 was retrospectively reviewed. Lesion volume at initial treatment and each follow-up was calculated by using the following formula: length × width × height / 2. Volume changes were correlated with patient demographics, histopathology, and radiation treatment variables. RESULTS: Thirty-two percent of lesions increased in volume following radiosurgery. Clinically, this translated into 54% of patients having ≥1 of their lesions increase in size. This increase begins at 6 weeks and can last beyond 15 months&#039; post-SRS. Male sex (P = .002), mean voxel dose &amp;lt;37 Gy (P = .009), and initial treatment volume &amp;gt;500 mm3 (P &amp;lt; .001) are associated with posttreatment increases in tumor size. Median survival following radiosurgery was 9.5 months for patients with all lesions exhibiting stable/decreased volumes, &amp;gt;18.4 months for patients with all lesions exhibiting increased volumes, and 16.4 months for patients with mixed lesional responses. CONCLUSIONS: Most metastatic lesions are stable or smaller in size during the first 36 months post-SRS. However, a transient increase in volume is seen in approximately one-third of lesions. Sex, treatment dose, initial lesion size, and histopathology all correlate with variations in lesion volume post-SRS. The longer the patient survives, the more likely an increase in lesion size will be seen on follow-up imaging. DWIdiffusion-weighted imagingFDG-PETfluorodeoxyglucose–positron-emission tomographyFLAIRfluid-attenuated inversion recoveryGKGamma KnifeMPRAGEmagnetization-prepared rapid acquisition of gradient echoSRSstereotactic radiosurgeryWBRTwhole-brain radiation therapy