Negative prostatic biopsies in patients with a high risk of prostate cancer. Is the combination of endorectal MRI and magnetic resonance spectroscopy imaging (MRSI) a useful tool? A preliminary study.

OBJECTIVE: Repeated biopsies in patients with a high risk of prostate cancer only allow a small proportion of new cancer diagnosis. The aim of this study was to evaluate the use of combined MRI and magnetic resonance spectroscopy imaging (MRSI) for these patients.
METHODS: Between April 2003 and April 2004, 42 patients with negative multiple cores prostatic biopsies and serum PSA>4 ng/ml underwent a combined MRI/MRSI analysis. Suspicious zones on standard MRI included low intensity signals on T2 weighted images. A high choline+creatine-to-citrate ratio defined a MRSI suspicious zone. A 10 cores following peripheral biopsy scheme was done to which were added supplementary biopsies on the MRI/MRSI suspicious zones.
RESULTS: The mean age was 62.3 years (51-74), the mean pre-biopsy serum PSA was 12 (3.87-35), the mean free/total PSA ratio was 11% (5-20). The mean number of previous prostate biopsy rounds was 2.04. 15 prostate cancers were diagnosed (35.7%). In 9 cases, abnormal MRI/MRSI findings and positive biopsy sites were located on the same prostatic zones. In 5 cases, MRSI alone located the positive biopsy zones. Sensitivity of combined MRI/MRSI in this study was 73.3%; specificity, positive predictive value, negative predictive value and accuracy were 96.3%, 91.6%, 86.6% and 88% respectively.
CONCLUSIONS: This preliminary study shows that the combination of MRI and MRSI might be able to guide and therefore limit the number of iterative biopsies and cores for patients who are at high risk of having a prostate cancer. In some cases, MRSI alone allows identification of neoplasic prostatic zones. Other studies are needed to confirm these data.