Diffusion-weighted imaging of prostate cancer on 3T MR: Relationship between apparent diffusion coefficient values and Ki-67 expression

Rationale and objectives: To investigate the relationship between apparent diffusion coefficient (ADC) values and the Ki-67 staining index (Ki-67 SI), a tumor proliferation marker, in prostate cancer (PCa).

Materials and methods: Forty-three patients with PCa and thirty-six patients with benign prostatic hyperplasia (BPH) underwent diffusion-weighted (DW) imaging on 3T magnetic resonance (MR) with pelvic phased-array coil. The ADC values of PCa were calculated from two DW images (b = 0, 800 s/mm(2)). Immunohistochemical staining for Ki-67 was used to determine the Ki-67 SI of PCa and BPH. The Pearson correlation test was used to examine the relationship between ADC values and the Ki-67 SI. The ADC values of PCa with different level of Ki-67 SI were compared using an independent-sample t-test.

Results: The mean (±standard deviation [SD]) Ki-67 SI of PCa (7.23 ± 5.29%) was higher than that of BPH (2.11 ± 1.90%) (P < .001). The mean (±SD) ADC value (10(-3) mm(2)/s) of PCa (0.850 ± 0.155) was lower than that of BPH (1.173 ± 0.245) (P < .001). The ADC values of PCa were negatively correlated with the Ki-67 SI (r = -0.459, P = .002). The mean ADC values of PCa with Ki-67 >3.5% and ≤3.5% were (0.803 ± 0.094) and (0.936 ± 0.208), respectively. The former was significantly lower than the latter (P = .031). The ADC values of PCa with Ki-67 >7.1% and ≤7.1% were (0.779 ± 0.081) and (0.906 ± 0.178), respectively. The difference was significant (P = .004).

Conclusion: The ADC values of PCa could reflect the tumor proliferative activity and the differentiated degree of PCa.