Material characterization of ex vivo prostate tissue via spherical indentation in the clinic

Background: The mechanical characterization of prostate tissue has not received much attention and is often disconnected from the clinic, where samples are readily attained. Methods: We developed a spherical indenter for the clinic to generate force-displacement data from ex vivo prostate tissue. Indentation velocity, depth, and sphere diameter, and four means of estimating elastic modulus (EM) were validated. EM was then estimated for 26 prostate specimens obtained via prostatectomy and 6 samples obtained from autopsy. Prostatectomy prostates were evaluated clinically upon digital rectal exam and pathologically post-extirpation. Findings: Whole-mount measurements yielded median EM of 43.2. kPa (SD = 59.8. kPa). Once sliced into cross-sections, median EM for stage T2 and T3 glands were 30.9 and 71.0. kPa, respectively, but not significantly different. Furthermore, we compared within-organ EM difference for prostates with (median = 46.5. kPa, SD = 22.2. kPa) and without (median = 31.0. kPa, SD = 63.1. kPa) palpable abnormalities. Interpretation: This work finds that diseased prostate tissue is stiffer than normal tissue, stiffness increases with disease severity, and large variability exists between samples, even though disease differences within a prostate are detectable. A further study of late-stage cancers would help to strengthen the findings presented in this work.