title: The predictive capacity of apparent diffusion coefficient (ADC) in response assessment of brain metastases following radiation.
abstract: To investigate the predictive capacity of the apparent diffusion coefficient (ADC) as a biomarker of radiation response in brain metastases. Seventy brain metastases from 42 patients treated with either stereotactic radiosurgery or whole brain radiotherapy were imaged at baseline, 1 week, and 1 month post-treatment using diffusion-weighted MRI. Mean and median relative ADC for metastases was calculated by normalizing ADC measurements to baseline ADC. At 1 year post-treatment, or last available follow-up MRI, volume criteria determined final tumour response status. Uni- and multivariate analysis was used to account for factors associated with tumour response at 1 week and 1 month. A generalized estimating equations model took into consideration multiple tumours per subject. Optimal thresholds that distinguished responders from non-responders, as well as sensitivity and specificity were determined by receiver operator characteristic analysis and Youden's index. Lower relative ADC values distinguished responders from non-responders at 1 week and 1 month (P < 0.05). Optimal cut-off values for response were 1.060 at 1 week with a sensitivity and specificity of 75.0 and 56.3 %, respectively. At 1 month, the cut-off was 0.971 with a sensitivity and specificity of 70.0 and 68.8 %, respectively. A multivariate general estimating equations analysis identified no prior radiation [odds ratio (OR) 0.211 and 0.137, P = 0.033 and 0.0177], and a lower median relative ADC at 1 week and 1 month (OR 0.619 and 0.694, P = 0.0036 and 0.005), as predictors of tumour response. Lower relative ADC values at 1 week and 1 month following radiation distinguished responders from non-responders and may be a promising biomarker of early radiation response.
authors.affiliation: Department of Medical Imaging, Sunnybrook Health Sciences Center, University of Toronto, Toronto, ON, Canada.
authors.forename: Raphael
authors.initials: R
authors.lastname: Jakubovic
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Zhou
authors.affiliation: Department of Medical Imaging, Sunnybrook Health Sciences Center, University of Toronto, Toronto, ON, Canada.
authors.forename: Chris
authors.initials: C
authors.lastname: Heyn
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Hany
authors.initials: H
authors.lastname: Soliman
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada.
authors.forename: Liyang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Medical Imaging, Sunnybrook Health Sciences Center, University of Toronto, Toronto, ON, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Aviv
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada. arjunsahgal@yahoo.com.
authors.forename: Arjun
authors.initials: A
authors.lastname: Sahgal
mesh_terms: D001932:Brain Neoplasms / Q000532:radiotherapy* / Q000556:secondary* / Q000601:surgery; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D016634:Radiosurgery; D011878:Radiotherapy; D016896:Treatment Outcome
keywords: ADC; Brain metastases; MRI; Response; Stereotactic radiosurgery