Abstract
PurposeThe sensitivity of the magnetization transfer ratio (MTR) and apparent diffusion coefficient (ADC) for early detection of brain metastases was investigated in mice and humans.MethodsMice underwent MRI twice weekly for up to 31 d following intracardiac injection of the brain‐homing breast cancer cell line MDA‐MB231‐BR. Patients with small cell lung cancer underwent quarterly MRI for 1 year. MTR and ADC were measured in regions of metastasis and matched contralateral tissue at the final time point and in registered regions at earlier time points. Texture analysis and linear discriminant analysis were performed to detect metastasis‐containing slices.ResultsCompared with contralateral tissue, mouse metastases had significantly lower MTR and higher ADC at the final time point. Some lesions were visible at earlier time points on the MTR and ADC maps: 24% of these were not visible on corresponding T2‐weighted images. Texture analysis using the MTR maps showed 100% specificity and 98% sensitivity for metastasis at the final time point, with 77% sensitivity 2–4 d earlier and 46% 5–8 d earlier. Only 2 of 16 patients developed metastases, and their penultimate scans were normal.ConclusionsSome brain metastases may be detected earlier on MTR than conventional T2; however, the small gain is unlikely to justify “predictive” MRI. Magn Reson Med 77:1987–1995, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Highlights
Brain metastases (BM) develop in 20 to 40% of all cancer patients and are a major cause of morbidity and mortality[1]
Of the 29 mice injected with MDA-MB231-BR cells and scanned on multiple occasions, 14 developed brain metastases (48%)
Once the metastases were seen, we examined the same regions on earlier scans to see whether there were subtle changes that could be visualized using our methods (as a result of, for instance, the establishment of premetastatic niches [29])
Summary
Brain metastases (BM) develop in 20 to 40% of all cancer patients and are a major cause of morbidity and mortality[1]. Neurosurgery or stereotactic radiosurgery may be possible in selected patients, but for the majority, treatment options include steroids, whole brain radiotherapy, and supportive care with median survival measured in a small number of months. The high incidence of BM is perhaps the result in part of the use of targeted drugs such as monoclonal antibodies: These are effective in controlling extracranial metastatic disease and thereby extending survival, but they do not cross the blood-brain barrier and are ineffective against BM. In light of the very high incidence of BM for patients with small cell lung cancer (SCLC), prophylactic cranial irradiation (PCI) was introduced into the routine management of patients with limited stage [2] and extensive stage [3] disease, and it significantly improves overall survival in addition to significantly reducing the incidence of BM.
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