Comparison of diffusion weighted imaging and transrectal ultrasound-guided biopsy in predicting aggressiveness of prostate cancer

Abstract

Objective To retrospectively evaluate the utility of apparent diffusion coefficient (ADC) values in predicting aggressiveness of prostate cancer.Comparison was made with transrectal ultrasound-guided biopsy Gleason scores (GS) and prostatectomy GS.Methods Diffusion weighted images of 51 patients with biopsy-proven prostate cancer were obtained using 1.5 T MR with a pelvic phased-array coil.Regions of interest (ROIs) were drawn on areas of the suspicious lesion and the ADC values were calculated.The correlations between the ADC values and prostatectomy GS were assessed with Pearson correlation.The relationship between biopsy GS and prostatectomy GS were also evaluated.Meanwhile,receiver operating characteristic (ROC) curves were used to determine the ability of ADC values and biopsy GS in differentiating low-grade prostate cancer from intermediate/high grade prostate cancer.Results The accuracy of transrectal ultrasound-guided biopsy in predicting prostatectomy GS was 41.2％(21/51).Compared with prostatectomy GS,up to 11.8％ of the patients (n =6) was overestimated by biopsy,while 47.0％ (n =24) were underestimated.These 51 patients had a mean ADC value of (0.974 ±0.194) × 10-3 mm2/s.The mean ADC value of intermediate/high-grade tumors (n =35) was (0.907 ±0.160) ×10-3 mm2/s while that of low-grade tumors was (1.121 ±0.185) × 10-3 mm2/s (n =16).A significant negative correlation was found between mean ADC values of suspicious lesions and their prostatectomy GS (r =-0.761,P ＜ 0.01).No significant correlation was found between biopsy GS and prostatectomy GS (r =0.187,P =0.189).The area under the ROC curves of ADC and biopsy GS was 0.827 and 0.689,respectively.Conclusion The ADC values of cancerous areas in prostate perform better than biopsy GS in predicting aggressiveness of prostate cancer. Key words: Prostatic neoplasms; Magnetic resonance imaging; Comparative study