Canada: High-resolution transrectal micro-ultrasound (MicroUS) is highly sensitive in detecting index lesions in the prostate gland and very accurate in identifying index lesions in the peripheral zone, states an article published in the Urology.
Prostate cancer is the second most commonly diagnosed cancer and one of the leading causes of cancer death among men worldwide. It occurs in the prostate, which is a small walnut-shaped gland in males. It is treatable if diagnosed early. The index lesion is the largest prostatic tumor with the highest histologic grade; it is the most clinically significant tumor. Cancer volume has been proposed as an important determinant of biochemical failure and PCa progression. Standard transrectal ultrasound (8–12 MHz) used in prostate biopsy lacks the resolution to effectively identify many index prostate cancer lesions.

Callejas MF, University of Toronto, Canada, and his research team conducted a study to determine the detection of clinically significant prostate cancer (csPCa) index lesion using high-resolution transrectal micro-ultrasound (MicroUS) applying PRI-MUS (Prostate Risk Identification using Micro Ultrasound) score v1.0.
Researchers included 25 participants who underwent radical prostatectomy following biopsy and MicroUS assessment. The median age was 65.5 years (range 56 - 74). Median Prostate-specific antigen ( PSA) was 6.45 ng/dL (range 2 - 31.72). an experienced radiologist retrospectively reviewed the MicroUS dynamic cine loops of these patients. Suspicious sites were assigned a PRI-MUS score. Radical prostatectomy specimens were examined with the quarter mount technique. The detection rate of csPCa index lesion [Grade Group (GG) ≥2] by MicroUS was assessed at a patient level.
Key findings of the study,
• 2 of 25 patients did not have csPCa (GG1 disease) on radical prostatectomy.
• MicroUS visualized 87% of the csPCa index lesions [median length 9 mm].
• All identified lesions were categorized with a PRIMUS score of 4 or 5.
• The 3 missed index lesions were in the transition zone [median length 10.5 mm].
• MicroUS missed 11 non index csPCa in 9 participants [median length 1.5 mm]. Of these, 8 were GG2, two GG3, and one GG5. MicroUS identified the csPCa index lesion in all 9 of these men.
Based on the study results, the authors conclude that high-resolution transrectal micro-ultrasound (MicroUS) showed 87% sensitivity in detecting index lesions in the prostate gland and identified all the lesions in the peripheral zone. High-resolution transrectal MicroUS demonstrated index prostate cancer lesions detection rates that were comparable to the rates demonstrated by multiparametric MRI. This new technology may help urologists to identify and target index prostate cancer lesions during prostate biopsy.
Reference:
Callejas MF, Klein EA, Truong M, Thomas L, McKenney JK, Ghai S. Detection of clinically significant index prostate cancer using micro-ultrasound: correlation with radical prostatectomy. Urology. 2022 Jul 14:S0090-4295(22)00592-1. doi: 10.1016/j.urology.2022.07.002.