The predictive and prognostic value of diffusion weighted magnetic resonance and FDG PET/CT imaging in nasopharyngeal carcinoma

PURPOSE In this study, we aimed to analyse the effect of metabolic activity and diffusion limitation on treatment responses and prognoses of patients with the diagnose of nasopharyngeal cancer treated with chemoradiotherapy. METHOD The records of 43 patients with nasopharyngeal cancer treated with chemoradiotherapy between 2008-2015 at Akdeniz University Medical Faculty Department of Radiation Oncology were reviewed retrospectively. Positron emission tomograpy/computarized tomograpy (PET/CT) and diffusion weighted magnetic resonance (DWMR) images obtained before and 3 months after treatment were analysed. Standardized uptake values (SUVmax, SUVmean, MTV, TLG) parameters indicating metabolic activity and apparent diffusion coefficient (ADC) values reflecting diffusion limitation were established from PET/CT and DWMR, respectively. The relation between ADCmean and SUV parameters was tested and the effects of these parameters on treatment response and prognose were studied. RESULTS Average follow-up was 46 months. While 36 patients received concurrent chemoradiotherapy, 17 patients received neoadjuvan chemotherapy (CT). Adjuvant CT was given to 14 patients. Radiotherapy was given with intensity modulated radiotherapy technique and 70 Gy was applied in 2 Gy fractions for primary neoplasm and metastatic lymph nodes. When the parameters of DAMRG, PET/BT before and 3 months after treatment analysed separately for the primary neoplasm and metastic lymph nodes, high ADCmean of primary neoplasm at diagnosis was determined to affect treatment response negatively but disease free survival rate positively (p<0.05). On the other hand higher percentage response of ADCmean correlated with higher survival (p<0.05). ADCmean values of lymph nodes were not found to effect treatment response and survival. When we analysed the effects of SUV parameters; we observed that the responses of primary tumors with high SUV parameters responded better (p<0.05). However disease-free-survival rates of the tumors with high SUVmax values were lower (p<0.05). Interestingly, the high SUV parameters of lymph nodes affected positively both response and survival which is different from that of primary tumor (p<0.05). When the rates of responses were examined it was seen that the low values of SUVmax, SUVmean, and TLG percantage responses affect disease-free-survival negatively (p<0.05). SUVmax and SUVmean were found to be correlated with the stage of T. CONCLUSION ADC and SUV parameters are the important parameters which affect the response of tumor and disease-free-survival in nasopharynx cancer. Interpreting ADC and SUV parameters together may provide further information about response and prognosis. In the short run, it will be possible to obtain these two parameters' results in the same verification and evaluate the situation of patients better with the increasing using of PET/MR in Turkey.