Diffisuion mr imaging for evaluation of response to treatment in patients with lung cancer

DIFFISUION MR IMAGING FOR EVALUATION OF RESPONSE TO TREATMENT IN PATIENTS WITH LUNG CANCER Purpose: The purpose of this study is to observe the change of ADC value after chemotherapy and to determine the ability of the change of ADC value to predict treatment response in lung cancer at the early stage of chemoradiotherapy. Material and Methods: This prospective study was carried out between February 2015 – December 2015 on patients with pathologically confirmed diagnosis of lung cancer which are stage III-IV lung cancer. The study included 25 patients with lung cancer who underwent T2-weighted MR, DWI, CT and FDG PET/CT and 11 patients were treated with chemoradiotherapy. The all of these 11 patients underwent chest DWI imaging and CT after the chemoradiotherapy. Posttherapy; DWI was repeated one week after end of the two cycles of chemotherapy and two weeks after end of the radiotherapy while posttherapy CT was performed four or five weeks after therapy. Patients had not received any treatment before imaging and no more than two or three weeks between studies. Signal intensities (SIs) were evaluated in diffusion-weighted MR images that were obtained with b=0 and 1000 s/mm² values. Apparent diffusion coefficient (ADC) values were calculated by using diffusion weighted images. Pretherapy ADCmin, ADCmean and SUVmax values compared with each other. Posttherapy tumor's ADCmin, ADCmean values and diameters compared with pretherapy measurements. Diameter changes were evaluated according to RECIST (Response Evaluation Criteria in Solid Tumors) criteria. The ''pearson's correlation coefficient'' was applied to assess of correlation between SUVmax, ADCmin and ADCmean values. To treatment early response prediction ability of ADC values were investigated. The statistical significance was determined using the ''pearson's correlation coefficient'' and the ''spearsman's rho'' tests. Findings: Data analysis revealed a statistically insignificant inverse correlation between of the pretherapy ADCmin and SUVmax (r = -0,36; p = 0.077) with ADCmean and SUVmax (r = -0,283; p = 0.170), (n=25). Posttherapy repeated measures revealed that increased ADCmin values were significantly higher with change of tumor large size (r =−0.872; p = 0.000) and median size (r =−0.847; p = 0.001) of tumor on CT. No significant correlation was found for the comparison of ADCmin with short tumor size (r =−0.410; p = 0.210), ADCmean with large tumor size (r =−0.460; p = 0.154), ADCmean with average tumor large size (r =−0.536; p = 0.89) and ADCmean with tumor short size (r =−0.136; p = 0.689) (n=11). Result: DWI with ADC measurement might represent a new prognostic marker in lung cancer. Repeated measures revealed that the increased ADCmin values were significantly higher in good responders with a large reduction in tumor size on CT. DWI may have better potential than CT and FDG PET/CT for prediction of tumor response to therapy in lung cancer patients. We think that the change of ADC values may be a sensitive indicator to predict early response to chemotherapy in lung cancer. Keywords: diffusion, apparent diffusion coefficient, lung cancer, responce to treatment, magnetic resonance imaging