Prostate cancer is the most common solid organ cancer in men (1). The main objective of current non-invasive imaging techniques is to detect early-stage disease that is biologically aggressive in an attempt to offer timely curative treatments. The currently used screening and diagnostic tools include digital rectal examination; serum prostate-specific antigen (PSA) and non-targeted transrectal ultrasound (TRUS)–guided biopsy (3). Because of the limitations and poor specificity of the available diagnostic tools, significant efforts are being made into improving prostate cancer detection. It has been postulated that multiparametric MRI is useful in the detection and risk stratification of prostate cancer (4) and also, that MRI can serve as a guide to adequately sample suspicious lesions in the prostate (5). Therefore, the objective of this study is to investigate Magnetic Resonance Spectroscopic Imaging (¹H-MRSI) in suspicious prostate lesions as an imaging biomarker of malignancy, and to correlate the values with the results of targeted prostate sampling under MRI-guidance.IRB approved HIPAA compliant retrospective review of a 12-month period prospective cohort of patients presenting with persistently elevated or rising serum prostate specific antigen (PSA) and at least one lesion suspicious for prostate cancer that underwent MRI guided targeted biopsy. Diagnostic and interventional procedures were performed using a 32-element surface pelvic array coil on a 3T MAGNETOM Trio system (Siemens Medical Solutions, Erlangen, Germany). The spectroscopic imaging was performed with the spectroscopic software provided by the MR scanner (Symphony; Siemens Medical Solutions, Erlangen, Germany), using the surface coil. The software acquires data with point-resolved spatially localized spectroscopy (PRESS) (TR = 750 ms / TE = 145 ms / NSA = 6 / FA = 90º / voxel size = 7 x 7 x 7 mm / TA = 9:54 min). By using spectral-spatial pulses, choline, creatine, and citrate were excited. Water and lipids were suppressed with a shim around the spectral box. The box was placed on the previously obtained transverse T2 weighted images. Shimming algorithms provided by the manufacturer automatically optimized the magnetic field homogeneities. Subsequent targeted biopsy was performed following transrectal placement of a Dyna-TRIM biopsy system (Invivo, Gainesville, FL). Pre-procedural imaging allowed identification of the transrectal fiducial line, target lesions, and tridimensional trajectory. Pathology results per lesion were correlated to pre-procedural metabolite ratio (Cho+Cr/Ci) utilizing the Pearson correlation coefficient. Receiver operating characteristic (ROC) curves were made to analyze ¹H-MRSI performance in discriminating low- and high-grade tumors (α=0.05).Thirty-five consecutive patients were recruited (mean age 63, range 55-82). Average PSA level was 9.3 ng/mL (median 7.76 ng/mL; SD 6.4 ng/mL). 179 suspicious lesions were successfully biopsied (Average number of lesions per patient 5, range 2-8) and all samples were deemed diagnostic. Overall cancer detection rate was 19/35 (54.2%). Pathology results were benign in 133 lesions (74.3%), and malignant in 43 lesions (24.7%), with low-grade cancer (Gleason score 6) in 12/179 (6.7%); and intermediate-high-grade cancer (Gleason score > 7) in 31/179 (17.3%). Mean metabolite ratio for cancerous lesions was 7.33 (±SD 32.99); and mean metabolite ratio for benign lesions was - 6.62 (±SD 9.99). No correlation was found between the spectroscopy metabolite ratio score and the presence of malignancy (r = 0,013). For a cut-off point of –2.56, ROC curve analysis demonstrates an AUC = 0.686 with a sensitivity of 65.6% and a specificity of 61.8% (Figure 1). Figure 2 illustrates a positive spectroscopy.This investigation demonstrates a poor performance of 1H-MRSI as a biomarker in predicting malignancy in patients with persistently elevated or rising serum prostate specific antigen (PSA) levels and suspicious focal prostate abnormalities undergoing targeted tissue sampling under MRI guidance.