New aspects in shear-wave elastography of prostate cancer

Aim: This study was designed to evaluate the performance of shear-wave elastography as a diagnostic tool for prostate cancer in a larger cohort of patients than previously reported. Patients and methods: Seventy-three patients with suspected prostate carcinoma were investigated by ultrasound elastography followed by directed biopsy. The elastographic and histological results for all biopsies were compared. Results: After exclusion of invalid and non-assessable results, 794 samples were obtained for which both a histological assessment and an elastometric result (tissue stiffness in kPa) were available: according to the histology 589 were benign and 205 were malignant. Tissue elasticity was found to be weakly correlated with patient's age, PSA level and gland volume. ROC analysis showed that, for the set of results acquired, elastometry did not fulfil literature claims that it could identify malignant neoplasia with high sensitivity and specificity. However, it did show promise in distinguishing between Gleason scores <= 6 and >6 when malignancy had already been identified. Unexpected observations were the finding of a smaller proportion of tumours in the lateral regions of the prostate than generally expected, and also the observation that the elasticity of benign prostate tissue is region-sensitive, the tissue being stiffest in the basal region and more elastic at the apex. Conclusions: Shear-wave elastography was found to be a poor predictor of malignancy, but for malignant lesions an elasticity cut-off of 80 kPa allowed a fairly reliable distinction between lesions with Gleason <= 6 and those with Gleason >6. We demonstrate an increase in elasticity of benign prostate tissue from the basal to the apical region.