Introduction:

MRI-US fusion biopsy (Fbx) demonstrates improved clinically significant prostate cancer detection rates (CDR) over 12-core systematic transrectal ultrasound (TRUS) biopsy. However, some have argued that among patients with smaller prostate glands, that targeted biopsy may not provide additional diagnostic value over TRUS biopsy.

Methods:

Patients were enrolled in a prospectively designed cohort study assessing cancer detection rates by Fbx and TRUS. All patients underwent both biopsy modalities in the same setting and the CDR by each modality were assessed. Following data collection, patients were stratified in to quintiles by prostate volume and CDR by Fbx and TRUS biopsy were compared.  The primary outcome was the difference in CDR of clinically significant cancer, defined as Gleason ≥7. The difference in CDR between the two groups were compared using the chi-square test with a result of p < 0.05 considered statistically significant.

Results:

Between 2007 and 2019, 2103 men underwent both TRUS and MRI-US fusion biopsy. Of these men, 1992 of them had a prebiopsy prostate volume measurement on MRI and were included in this study. Median age and median PSA at the time of biopsy were 64 (IQR 58-68) and 6.7 ng/dL (IQR 4.6-10.3), respectively. Median prostate volume on MRI (59 cc, IQR 37-71) and median number of Fbx targets (4 IQR 2-6) were assessed. The difference in CDR between TRUS biopsy and Fbx for the entire cohort was 6.8% (30.9% vs 37.8%, p < 0.001). Upon stratification of patients based on prostate volume, Fbx had superior CDR for prostates with volumes up to 30 cc (46.6% vs. 61.2%, p < 0.001), 31 to 60 cc (36.9% vs. 45.0%, p < 0.001), and 61 to 90 cc (18.8% vs. 24.6%, p = 0.044). Prostate volumes greater than 90 cc did not show a statistically significant difference in CDR between the two biopsy techniques. When analyzing CDR for Gleason 8 or greater disease, Fbx had improved cancer detection rates for prostates with volumes 0 to 30 cc (14.9% vs. 20.0%, p = 0.045) and 31 to 60 cc (11.3% vs. 17.7%, p < 0.001).

Conclusion:

Contrary to common belief, MRI-targeted biopsy yields the highest cancer detection rates and greatest increase in cancer detection rates relative to TRUS biopsy among patients with a prostate volume of 0-60 cc. MRI targeted biopsies should not be skipped among patients with smaller prostate glands due to the belief that systematic biopsy adequately samples smaller prostates.

Funding: N/A