Transrectal Ultrasound Versus MRI for Estimating Prostatic Volume

A comparative effectiveness study offered new insights into the more optimal method of determining prostatic volume for patients with prostate cancer. Results of the study were presented at the 2023 American Society of Clinical Oncology Genitourinary Cancers Symposium.

While transrectal ultrasound (TRUS) during prostate biopsy has been considered standard of care for estimating prostatic volume, prostate magnetic resonance imaging (MRI) has come into favor in recent years. Further research is needed to determine whether clinically significant differences exist between the 2 imaging modalities.

Wyatt Whitman, MD, and colleagues designed a study to compare prostate volumes from TRUS and MRI with gross specimens after prostatectomy. A total of 83 patients (median age, 65.47 years) who underwent radical prostatectomy for prostate cancer from 2017 through 2022 were sampled. TRUS and MRI measurements closest to the date of surgery were obtained and then compared with gross prostate specimens after surgery.

Results of the analysis showed that TRUS volume differed significantly from gross specimen volume (average, –4.56 mL; P=.017) and gross specimen weight (average, –14.31 g; P<.001). Conversely, MRI gross specimen volume did not differ significantly (average, –0.56 mL; P=.771) but was significantly different from prostate weight (average, –10.32 g; P<.001).

Notably, when compared with one another, TRUS and MRI significantly differed on average by –4 mL (P=.033).

“Urologists should be aware of potential inaccuracies when assessing preoperative prostate volume with TRUS and recognize MRI is the best predictor of size,” researchers concluded. “While imperfect, TRUS is still relatively accurate [at] measuring prostate volume, and given its ease of availability and cost, we feel it is a useful modality to determine prostate size.”