January 24, 2022

MRI–ULTRASOUND FUSION–TARGETED TRANSPERINEAL PROSTATE BIOPSY COMPLEMENTS STANDARD BIOPSY FOR DETECTING PERINEURAL INVASION

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KEY FINDINGS

• This retrospective study compared standard transrectal ultrasound-guided 20-core systematic prostate biopsy (SBx) and MRI–ultrasound fusion–targeted transperineal biopsy (TBx) for their ability to detect perineural invasion (PNI)
  
• The study subjects were 238 men who had undergone the two procedures concomitantly and had been diagnosed with prostate cancer
  
• 32% of all patients had PNI detected by SBx and/or TBx, and that figure was higher than for SBx or TBx alone
  
• 38.5% of the 148 patients with clinically significant prostate cancer had PNI detected by SBx and/or TBx, again more than with SBx or TBx alone
  
• Subgroup analyses determined TBx has the ability to detect PNI more precisely than SBx in a smaller tumor and can improve on the rate of PNI detection by SBx
  

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In 7%–33% of prostate biopsies, perineural invasion (PNI) is detected—cancer tracking along or around a nerve within the perineural space. The perineural space seems to be a low-resistance exit route for cancer cells, as biopsy PNI has been linked with extraprostatic extension and metastasis.

Most data available on biopsy PNI in prostate cancer were obtained using the traditional biopsy approach: transrectal ultrasound-guided 12-core systematic biopsy (SBx). However, MRI–ultrasound fusion–targeted transperineal biopsy (TBx) is now favored for its lower risk of complications and feasibility for use in outpatient clinics under local anesthesia.

Chin-Lee Wu, MD, PhD, associate pathologist and director of Genitourinary Pathology Services at Massachusetts General Hospital and the Mass General Cancer Center, and Douglas M. Dahl, MD, urologic surgeon in the Department of Urology at Mass General and chief of the Division of Urologic Oncology at the Mass General Cancer Center, and colleagues recently became the first to compare the PNI detection rate for SBx and TBx. In Human Pathology, they say TBx complements and improves on SBx for this purpose.

Study Methods

The researchers reviewed a database of 301 men with prostate cancer who underwent concomitant transperineal TBx and standard 20-core template SBx between September 2019 and February 2021. All patients had had one or more prostate lesions identified on multiparametric MRI.

238 patients were diagnosed with prostate cancer and were included in this study.

Detection of PNI

• Of all 238 patients with prostate cancer, 32% had PNI detected by SBx and/or TBx. SBx alone detected PNI in 24% and TBx alone detected it in 19% (P=0.45)
• Of 148 patients with clinically significant prostate cancer, 38.5% had PNI detected by SBx and/or TBx. SBx alone detected PNI in 32% and TBx alone detected it in 26% (P=0.56)

Compared with patients who were PNI-negative, patients who had PNI detected on SBx and/or TBx had significantly:

• Smaller prostate volume
• Larger index lesions
• Higher frequency of highly suspicious lesions (PI-RADS 5)
• More cancer-positive cores
• Higher cancer-positive core rate
• Higher percentage of cancer in cancer-positive cores
• Higher frequency of clinically significant cancer

Subgroup Analysis

The 31 patients who had PNI detected only by SBx showed a significantly higher number of cancer-positive cores and cancer-positive core rate than the 20 patients who had PNI detected only by TBx.

176 patients had prostate cancer diagnosed by both SBx and TBx. In this group TBx detected 19 cases with PNI (15%) that SBx missed and SBx detected 24 cases with PNI (18%) that TBx missed.

Implications for the Clinic
The increased PNI detection rate with concomitant SBx and TBx should improve the ability to select candidates for active prostate cancer surveillance and aid treatment.

The subgroup results indicate TBx has the ability to detect PNI more precisely than SBx in a smaller tumor and can improve on the rate of PNI detection by SBx.

Read the article on mass general.org.