Combination of 99mTc-labeled PSMA-SPECT/CT and Diffusion-Weighted MRI in the prediction of early response after carbon ion therapy in prostate cancer: a prospective study

Abstract Background The purpose of this study was to assess the potential of 99mTc-labeled PSMA-SPECT/CT and Diffusion-Weighted Image (DWI) for predicting treatment response after carbon ion radiotherapy (CIRT) in prostate cancer. Methods We prospectively registered 26 patients with localized prostate cancer treated with CIRT. All patients underwent 99m Tc-labeled PSMA-SPECT/CT and multiparametric MRI before and after CIRT. The tumor/background ratio (TBR) and mean apparent diffusion coefficient (ADC mean ) were measured on the tumor and the percentage changes between 2 time points (ΔTBR and ΔADC mean ) were calculated. Patients were divided into two groups: good response and poor response according to clinical follow-up. Results The median follow up time was 38.3months. The TBR was significantly decreased ( p =0.001), while the ADC mean was significantly increased compared with the pretreatment value ( p <0.001). The ΔTBR and ΔADC mean were negatively correlated with each other ( p = 0.002). On ROC curve analysis for predicting treatment response, the area under the ROC curve (AUC) of ΔTBR (0.867) for predicting good response was higher than that of ΔADC mean (0.819). The AUC of combined with ΔTBR and ΔADC mean (0.895) was higher than that of either ΔADC mean or ΔTBR alone. The combined use of ΔTBR and ΔADC mean showed 91.4% sensitivity and 95.2% specificity. Conclusions Our preliminary data indicate that the changes of TBR and ADC mean maybe an early bio-marker for predicting prognosis after CIRT in localized prostate cancer patients. In addition, the ΔTBR was a more powerful prognostic factor than ΔADC mean in prostate cancer treated with CIRT.