Potential of magnetic resonance spectroscopic imaging in predicting absence of prostate cancer in men with serum prostate-specific antigen between 4 and 10 ng/ml: a follow-up study.

OBJECTIVES Screening for prostate cancer using serum prostate-specific antigen (PSA) determination has a positive predictive value of only 30% to 42% for a PSA level between 4 and 10 ng/mL. Magnetic resonance spectroscopic imaging (MRSI), which identifies cancer on the basis of changes in cellular metabolite levels, might be able to identify patients with noncancerous PSA elevation and help avoid unnecessary biopsies. We tested this hypothesis by evaluating the incidence of prostate cancer in men with a PSA level of 4 to 10 ng/mL and a negative MRSI study. METHODS A total of 155 men underwent a three-dimensional proton MRSI of the prostate before transrectal ultrasound-guided biopsy for clinical indications. MRSI was performed using an endorectal coil on a 1.5-T magnetic resonance scanner. Patients with no voxels positive for malignancy underwent standard sextant biopsy, and additional MRSI-targeted biopsies were obtained in men with suspicious or malignant voxels. Patients with a biopsy negative for cancer underwent repeat serum PSA estimation every 6 months for a minimum of 18 months. RESULTS Of the 155 men, 36 (mean PSA level of 6.47 ng/mL, range 4.25 to 9.9) had no malignant voxels on MRSI. None of them were positive for cancer on biopsy. Of these 36 men, 26 completed at least 18 months (mean 26.9, range 18 to 44) of follow-up. Four patients required repeat biopsies and one, with a persistently elevated PSA level was diagnosed with prostate cancer 29 months after the initial MRSI. CONCLUSIONS The results of our study have shown that prostate biopsy can be deferred in patients with an increased serum PSA of 4 to 10 ng/mL if their MRSI does not show any malignant voxels.