Diffusion magnetic resonance imaging as an evaluation of the response of brain metastases treated by stereotactic radiosurgery.
BACKGROUND
Loss of tumor cell results in a relative increase in extracellular space that may lead to alteration of ADC. Our purpose was to see if the ADC could be used, rather than methods depending on changes in tumor size, to predict treatment success after treatment of brain metastases with SRS.


METHODS
In a prospective study, the ADCs of 21 patients with 32 solid or solid-dominated brain metastases were taken before and 1 week, 1 month, and at 3-month intervals after SRS. Mean ADC values at the various time intervals were compared with each other to see whether or not the ADC might be used as an early indicator of treatment success or failure.


RESULTS
The mean pretreatment value of the ADC in the metastatic tumors was 1.05 +/- 0.12 x 10(-3) mm2/s (mean +/- SD). This value for the tumors rose significantly (P = .009) 7 days after SRS and continued to rise with time. Magnetic resonance imaging showed that 91% of these tumors had been controlled by the SRS. The ADC values in cystic/necrotic tumor tissue (2.13 +/- 0.18 x 10(-3) mm2/s) were significantly (P < .001) higher than those in noncentral necrotic tumor tissue (1.61 +/- 0.14 x 10(-3) mm2/s).


CONCLUSIONS
The ADC values might eventually be useful to evaluate treatment success-and in some patients, detected even at early time points-and to distinguish radiation-induced central necrosis from tumor regrowth in cases where other imagery is not definitive.
Department of Neurosurgery, Chung-Shan Medical University Hospital, Taichung 402, Taiwan. gk@csh.org.tw
Chuan-Fu
CF
Huang
His-Hsieh
HH
Chou
Hsien-Tang
HT
Tu
Ming-Shiang
MS
Yang
Jong-Kang
JK
Lee
Long-Yau
LY
Lin
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001932:Brain Neoplasms / Q000473:pathology* / Q000556:secondary / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D016634:Radiosurgery; D016896:Treatment Outcome; D047368:Tumor Burden