Combination Of Tc-99m-Labeled Psma-Spect/Ct And Diffusion-Weighted Mri In The Prediction Of Early Response After Carbon Ion Therapy In Prostate Cancer: A Non-Randomized Prospective Pilot Study

Purpose: The purpose of this study was to assess the potential of Tc-99m-labeled PSMA-SPECT/CT and diffusion-weighted image (DWI) for predicting treatment response after carbon ion radiotherapy (CIRT) in prostate cancer.Patients and Methods: We prospectively registered 26 patients with localized prostate cancer treated with CIRT. All patients underwent Tc-99m-labeled PSMA-SPECT/CT and multiparametric magnetic resonance imaging (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 before and after therapy (Delta TBR and Delta ADC(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 Delta TBR and Delta ADC(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 Delta TBR (0.867) for predicting good response was higher than that of Delta ADC(mean) (0.819). The AUC of combined with Delta TBR and Delta ADC(mean) (0.895) was higher than that of either Delta ADC(mean) or Delta TBR alone. The combined use of Delta TBR and Delta ADC(mean) showed 91.4% sensitivity and 95.2% specificity.Conclusion: 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 Delta TBR seems to be a more powerful prognostic factor than Delta ADC(mean) in prostate cancer treated with CIRT.