MR spectroscopy compared with DW-MRI and DCE-MRI at 3-tesla for the noninvasive prediction of short-term radiation response for patients with localized prostate cancer.

122 Background: PSA is not appropriate for assessing early radiation response for patients treated with and without hormones for prostate cancer. New biomarkers using multiparametric functional MR could be of value. To investigate the benefits of multiparametric functional MR for predicting radiation response during the first year after radiation therapy in prostate cancer patients. Methods: Between 01/2008 and 04/2010, 34 patients with a localized prostate cancer (T1-T3, N0) were prospectively enrolled in the ERIS trial. All patients underwent high dose IMRT with or without long term adjuvant hormonal therapy and were prospectively followed with MR spectroscopy, diffusion-weighted MRI and dynamic contrast-enhanced MRI at 3-Tesla without endorectal coil every 3 months up to 1 year. Patients were followed with DRE, PSA level every 3 months and with sextant-biopsy at 6 and 12 months following radiation. Choline and Citrate levels on MRS, apparent diffusion coefficient on DW-MRI and the slope of the contrast uptake on DCE-MRI were measured in the central gland and in the peripheral zone every 3 months over 12 months and compared with PSA nadir at 12 months (≤0.5 ng/mL vs. >0.5 ng/mL). Results: Cho, Cit and SCU significantly decreased over time whereas ADC remained stable. For the entire prostate at 3 months, the mean Cho level was higher in patients with PSA level >0.5 ng/mL at 1 year (10.1±3.0 vs. 6.6±2.5, p= 0.004). Similarly, Cit level was higher at 3 months for patients with PSA level > 0.5 ng/mL at 1 year (15.4±7.9 vs. 8.5±9.9, p= 0.0065). Neither ADC value nor contrast enhancement evaluated at each time interval was correlated with PSA at 1 year. Conclusions: Low Cho and Cit levels evaluated at 3 months are new markers for early success in prostate cancer patients treated with exclusive radiation therapy.