Predicting pathological tumor volume in prostate cancer lesions: A head-to-head comparison of micro-ultrasound vs. MRI.

Background And Objective Our objective was to evaluate the agreement between micro-ultrasound, MRI and pathological tumor and prostate volume. Methods Retrospective analysis of consecutive prostate cancer patients with MRI and micro-ultrasound diagnostic assessment who subsequently underwent radical prostatectomy. Tumor and prostate volume on micro-ultrasound and MRI imaging calculated by a dedicated software were compared to those of the prostatectomy specimen. Clinical, radiological, and pathological predictors of pathological tumor size were assessed. Results 65 men with a total of 104 lesions in the final pathology were included. Median micro-ultrasound tumor size was 1.05 ml (IQR 0.35-2.65). On MRI T2WI, DWI and ADC sequences median tumor volume was 0.73 ml (IQR 0.34-1.94), 0.94 ml (IQR 0.38-2.09) and 0.86 ml (IQR 0.42-1.58), respectively. The pathological median tumor size was 1.2 ml (IQR 0.2-3.9). On average, micro-ultrasound underestimated pathological tumor volume by 0.15 ml (P < 0.01) while DWI, the most precise MRI sequence underestimated tumor size by 0.26 ml (P < 0.01). The MRI and micro-ultrasound underestimated the pathological prostate volume by 6 ml (P < 0.01) and 3 ml (P = 0.47), respectively. Conclusions Both micro-ultrasound and MRI tend to slightly underestimate pathological tumor and prostate volume. Our study shows that both micro-ultrasound and MRI can be useful in the surgical planning although the underestimation of actual tumor size should be considered.