T2- and diffusion-weighted MR imaging to assess primary Gleason grade of prostate cancer

Whether combination of T2 signal intensity (SI) and apparent diffusion coefficient (ADC) allows for enhanced discrimination of Gleason scores (GS) in prostate cancer (PCA). Whether ADC allows for a discrimination of primary Gleason grade in patients with GS 7.

In step-sectioned prostatectomy specimens, 104 PCA foci of 66 patients were identified and graded according to the modified GS system. MR SI of prostate tumors standardized to obturator muscle (T2R Tm, ADC Tm, proposed ADC/T2R ratio) and relation to GS were tested using multivariate analysis with generalized estimation equations. Diagnostic accuracy was assessed by ROC-analysis.

T2R Tm SI has shown a borderline effect in predicting GS = 7 (p = 0.05), with very high T2R values (4th quartile) indicating a significantly lower probability of aggressive cancers (p = 0.009) compared to low T2R values (1st quartile; generalized linear modelling). We found an almost linear negative relationship of ADC Tm with LOGIT GS = 7 (p = 0.002). The effect (adjusted odds-ratio = 0.995) of ADC Tm for GS = 7 was almost identical for peripheral (PZ) and transitional zone (TZ) PCA (p = 0.013 and p < 0.0005, respectively). ROC-analysis of ADC showed an AUC of 78.9% for discrimination between GS=6 and=7.An ADC cut-off of < 1.005×10–3mm²/s indicated a GS = 7 (90.5% sensitivity, 62.5% specificity). Within GS = 7 PCA, an ADC >0.762 × 10 – 3 mm²/s indicated a primary Gleason grade of 3+4 (AUC = 69.6%). Tests for ADC/T2R-ratio did not provide additional information regarding PCA GS.

T2R SI does not provide additional information to predict PCA GS. However, ADC values have a good discriminatory power to predict GS and primary Gleason grades of GS = 7 PCA. Thus, ADC values should be considered as one important parameter for monitoring and stratification of PCA patients.