The predictive role of ADC values in prostate cancer patients treated with carbon-ion radiotherapy: initial clinical experience at Shanghai Proton and Heavy Ion Center (SPHIC).

Abstract

The aim of our study was to investigate the predictive role of apparent diffusion coefficient (ADC) values in evaluating for therapeutic changes from carbon-ion radiotherapy (CIRT) in prostate cancer patients. Thirty-one patients with prostate cancer treated with CIRT were enrolled in this retrospective study. Diffusion-weighted imaging (DWI) at 3-T was performed before and after CIRT. Before and after treatment, ADC values were measured in the tumors and in the benign tissues of the prostate, and serum prostate-specific antigen (PSA) levels were also assessed. We divided the patients into two groups: PSA response (PSA declines ≥50%) and non-PSA response group (PSA declines <50%). After CIRT treatment, the mean ADC value of the tumors (1.23×10(-3)mm(2)/s) was significantly increased as compared with the pretreatment value (1.07×10(-3)mm(2)/s) (p<0.001), whereas the ADC values of the benign tissues after treatment did not significantly increase compared with the pretreatment values (p=0.235). The mean PSA level was significantly reduced from 2.027ng/mL before treatment to 0.822ng/mL, respectively, after treatment (p=0.0063). The mean of ADC changes in PSA response group before and after CIRT was significantly higher than that in non-PSA response group (∆ADC value: 0.217 vs 0.097×10(-3)mm(2)/s, p=0.0229), and the rate of patients with PSA response was higher in the high ∆ADC group (∆ADC≥0.10) than in the low ∆ADC group (∆ADC<0.10) (72.7 and 33.3%, respectively), but marginally significant (p=0.056). Additionally, the baseline tumor ADC values revealed a negative correlation with changes in PSA levels after treatment (correlation coefficient, ρ=-0.524; p=0.0025). Our preliminary results suggest that ADC vales measurement may be a useful imaging biomarker for prediction and early assessment of therapeutic response of prostate cancer to CIRT.