Correlation between apparent diffusion coefficient value on diffusion-weighted MR imaging and Gleason score in prostate cancer

Objectives

To investigate whether diffusion-weighted imaging (DWI) apparent diffusion coefficient (ADC) correlates with prostate cancer aggressiveness and further to compare the diagnostic performance of ADC and normalized ADC (nADC: normalized to non-tumor tissue).

Patients and methods

Thirty pre-treatment patients (mean age, 69 years; range: 59–78 years) with prostate cancer underwent magnetic resonance imaging (MRI) examination, including DWI with three b values: 50, 400, and 800 s/mm². Both ADC and nADC were correlated with the Gleason score obtained through transrectal ultrasound-guided biopsy.

Results

The tumor minimum ADC (ADC_min: the lowest ADC value within tumor) had an inverse correlation with the Gleason score (r = –0.43, P < 0.05), and it was lower in patients with Gleason score 3 + 4 than in those with Gleason score 3 + 3 (0.54 ± 0.11 × 10³ mm²/s vs. 0.64 ± 0.12 × 10^?3 mm²/s, P < 0.05). Both the nADC_min and nADC_mean correlated with the Gleason score (r = –0.52 and r = –0.55, P < 0.01; respectively), and they were lower in patients with Gleason score 3 + 4 than those with Gleason score 3 + 3 (P < 0.01; respectively). Receiver operating characteristic (ROC) analysis showed that the area under the ROC curve was 0.765, 0.818, or 0.833 for the ADC_min, nADC_min, or nADC_mean; respectively, in differentiating between Gleason score 3 + 4 and 3 + 3 tumors.

Conclusion

Tumor ADC_min, nADC_min, and nADC_mean are useful markers to predict the aggressiveness of prostate cancer.