Combined magnetic resonance spectroscopy and dynamic contrast-enhanced imaging for prostate cancer detection

The use of magnetic resonance spectroscopy imaging (MRSI) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) have emerged as a valid diagnostic tools for prostate cancer (CaP).

Men with PSA levels below 10 ng/ml were enrolled in a prospective cohort study and underwent combined MRSI and DCE-MRI and transrectal ultrasound-guided prostate biopsy. Imaging was performed using a 1.5 T MR scanner (Symphony TIM; Siemens, Erlangen, Germany) with an endorectal coil (Medrad; Pittsburg, PA), inflated with 60 cc of air. Three-dimensional magnetic resonance spectroscopic data were acquired by using water and a lipid-suppressed double-spin-echo point-resolved spectroscopy sequence, which was optimized for quantitative detection of both choline and citrate. Dynamic contrast-enhanced MRI sequences were obtained with 3D T1-weighted FLASH images before and during rapid bolus administration of intravenous paramagnetic contrast medium gadoteric acid. Specificity, sensitivity, positive predictive value, negative predictive value, and accuracy were computed considering patients, each of the 2 lobes, each of the 6 sextants, and each 12th part of the prostate gland as single measurements.

Overall, 106 patients were included in the analysis. Median age was 65.9 years (range, 61.2-70.5 years) and median PSA level at study entry was 7.1 ng/ml (range, 2.5-9.9). CaP was detected at biopsy in 24 patients (22.6 % of the population) with a median Gleason score of 8 (range 4-10). Diagnostic accuracy of combined MRSI and DCE-MRI was 85%, sensitivity was 71%, and specificity was 48%, considering patients as single measurements, with a negative predictive value of 91%, but a positive predictive value of only 19%. Positive predictive value of the examination improved to 25% for patients who repeated biopsy.

Although this study confirms the potential usefulness of MRI for the diagnosis of CaP, the positive predictive value obtained was unacceptably low due to the high number of false positives recorded. Nevertheless, the high negative predictive value of the examination may serve to avoid unnecessary biopsies. Future research should be directed at assessing the value of combining MRI-based techniques with novel biochemical markers for the diagnosis of CaP in patients with low PSA levels.