Diffusion MR imaging findings in metastatic brain tumors

Cancer incidence is increasing day after day. There is so many prognostic factors for cancer patients but intracranical metastasis is one of the most important prognostic factor for quality of life. For adult patients, metastatic intracranial tumors seen 10 times more common than primary brain tumors. Metastatic tumors reflect the characteristics of primer tumor. The aim of this study, to compare quantitative apparent diffusion coefficient (ADC) values, signal intensity (SI) at T2 sequance and ADC ratio between calculated the counterpart of normal white matter ADC value and solid brain metastases which grouped primary malignancy diagnosis and also to determine the contribution of the diffusion MRI on routine magnetic resonance imaging (MRI) in the evaluation of brain metastases. This retrospective study, included 172 male, 127 women, total 299 patients who were applicant to Ankara Baskent University Hospital and Baskent University Adana Teaching and Research Hospital between January 2011 - May 2016. Patients choosed from a variety of clinical, primary malignancy with brain metastasis or first diagnosis applicant with complaints about the central nervous system, brain MRI taken and metastasis identified. The patients were classified according to their primary cancer. We measured mean ADC values (mADC), mean SI at T2 weighted sequences (mT2) and ADC ratio (rADC) that calculated mADC ratio the counterparty normal white matter's ADC value from the solid part of tumor which show the most contrast enhancement by using 1,5 Tesla (T) magnetic resonance (MR) scanner. The measurements were made by an experienced radiologist. ADC and T2 SI values of lung carcinoma were analyzed also because of the patients with metastatic carcinoma of the lung were a large portion of our patients. When compared between the groups of patients mADC average values of primary; small cell lung carcinoma (SCLC) mADC average value was shown to be lower than non-small cell lung carcinoma (NSCLC), breast carcinoma and renal cell carcinoma (RCC). In addition, the ADC rate that rADC value in SCLC was significantly lower than NSCLC (p <0.01) and no significant statistical relationship between the value of other diagnostic groups rADC. mADC average value of all metastases were observed to be lower than those of similar studies. There is no significant relationship between primary malignancy diagnosis and the number of intracranial metastatic lesions were not detected. When there was no relationship the number of lesions with mT2 and mADC value, rADC value was lower in patients with multiple lesions. Analysis conducted by the subtypes of lung carcinoma, SCLC's mADC value was lower than the value of lung adenocarcinoma and squamous cell carsinoma (SCC) and SCLC's rADC value was lower than the value of adenocarcinoma's. It was determined that no significant differences among groups of other variables. When the measurement of parameters analyzed the relationship between each other mADC-mT2 and rADC –mT2 has a positive corelation, but correlation between rADC -mT2 is weaker than mADC-mT2 (p <0.05). In conclusion, diffusion MRI findings of intracranial metastases, ADC features vary for primary malignancy diagnosis in our study. Because of applying in short time, be a non-invasive method,easy way and allows the quantitative measurement, DWI should be added conventional MRI for differential diagnosis of intracranial metastatic lesions for follow-up and response to treatment.