Research Article Diffusion-Weighted Magnetic Resonance Diagnosis of Local Recurrences of Prostate Cancer after Radical Prostatectomy: Preliminary Evaluation on Twenty-Seven Cases Salvatore Francesco Carbone, 1,2 Luigi Pirtoli, 1,3 Veronica Ricci, 1,2 Tommaso Carfagno, 1,3 Paolo Tini, 1,3 Augusto La Penna, 1,2 Eleonora Cacchiarelli, 1,2 and Luca Volterrani 1,2 1 Istituto Toscano Tumori, via Taddeo Alderotti 26/N, 50139 Florence, Italy 2 Unit of Diagnostic Imaging, University Hospital of Siena, Policlinico S. Maria alle Scotte, Viale Bracci, 53100 Siena, Italy 3 Unit of Radiotherapy, University Hospital of Siena, Policlinico S. Maria alle Scotte, Viale Bracci, 53100 Siena, Italy Correspondence should be addressed to Salvatore Francesco Carbone; fracarb@gmail.com Received 26 November 2013; Accepted 16 December 2013; Published 16 February 2014 Academic Editor: Giovanni Luca Gravina Copyright © 2014 Salvatore Francesco Carbone et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Objectives. To assess the diagnostic performance of difusion-weighted MR imaging (DWI) in patients afected by prostatic fossa (PF) relapse ater radical prostatectomy (RP) for prostatic carcinoma (PC). Methods. Twenty-seven patients showing a nodular lesion in the PF at T2-weighted MR imaging ater RP, with diagnosis of PC relapse established by biopsy or PSA determinations, were investigated by DWI. Two readers evaluated the DWI results in consensus and the apparent difusion coeicient (ADC) of the nodules, separately; a mean value was obtained (ADCm). Results. Relapses did not signiicantly difer in size in respect of postsurgical benign nodules. he DWI qualitative evaluation showed sensitivity, speciicity, accuracy, ppv, and npv values, respectively, of 83.3%, 88.9%, 85.2%, 93.7%, and 72.7% (100%, 87.5%, 95.6%, 93.7%, and 100%, for nodules >6 mm). he intraclass correlation coeicient (ICC) for ADC evaluation between the two readers was 0.852 (95% CI 0.661–0.935;  = 0.0001). he ADCm values for relapses and benign nodules were, respectively, 0.98 ± 0.21 × 10 −3 mm 2 /sec and 1.24 ± 0.32 × 10 −3 mm 2 /sec ( = 0.006). Sensitivity, speciicity, accuracy, ppv and npv of ADCm were, respectively, 77.8%, 88.9%, 81.8%, 93.3%, and 66.7% (93.3%, 87.5%, 85.4%, 93.3%, and 87.5% for nodules >6 mm). Conclusions. Difusion-weighted MR imaging is a promising tool in the management of a hyperintense nodule detected by T2-weighted sequences. his might have a relevant importance in contouring radiotherapy treatment volumes. 1. Introduction Prostate cancer (PC) is second in incidence among malig- nancies in men in Western countries [1]; the treatment of clinical localized disease is radical prostatectomy (RP) in many cases, and the decrease of the serum total prostate- speciic antigen (PSAt) values below 0.1-0.2 ng/mL within 1 month ater surgery documents complete tumour eradication [2]. However, a biochemical relapse occurs in 10%–53% of the patients undergoing RP within 5 years, deined as a PSAt increase in at least three consecutive samples [3]. his is usually the irst sign of recurrence, oten without any clinical or imaging evidence of a tumour mass; the clinical onset of recurrence follows ater a median of 5 years [4]. At present, the pattern of relapse (prostatic fossa recurrence versus metastatic disease) is established on the basis of PSAt increase (PSA velocity or PSA doubling time) with slow increasing PSAt values (i.e., doubling time >12 months) suggesting local disease. Early postoperative radiation therapy (RT) on PF may improve metastasis free and overall survival in cases at risk for LR [5]; however, in common practice, RT is performed Hindawi Publishing Corporation BioMed Research International Volume 2014, Article ID 780816, 8 pages http://dx.doi.org/10.1155/2014/780816