Targeted Biopsy Alone Detects Clinically Significant Cancer in Smaller Prostates
- This retrospective study of 301 patients compared the effectiveness of standard 20-core biopsy (SBx) alone, transperineal multiparametric MRI-targeted biopsy (TBx) alone, and the combination for detecting cancer in prostates of different volumes
- Regardless of the biopsy method, rates of detection of clinically significant cancer were notably higher in the smallest prostates (≤30 mL) than in the largest (>45 mL)
- Among patients with prostates ≤30 mL, detection rates were statistically similar with SBx only, TBx only, and the combined approach
- It seems feasible for TBx to replace the combination of TBx and SBx in smaller prostates
Conventional 20-core systematic prostate biopsy (SBx), which randomly samples the entire prostate, carries a substantial risk of overdiagnosing clinically insignificant prostate cancer, underdiagnosing clinically significant cancer, and causing complications such as bleeding and infection. Transperineal multiparametric MRI-targeted biopsy (TBx) requires only three cores yet increases the detection of clinically significant cancer.
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In a previous paper published in The Journal of Urology, researchers at Massachusetts General Hospital reported TBx and SBx to be complementary in detecting both overall and clinically significant prostate cancer. They recommended the concurrent use of both methods. But after a more recent analysis of the same cohort, the researchers have qualified that conclusion by stating that in small prostates (≤30 mL), it may be feasible to perform only TBx.
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, Chin-Lee Wu, MD, PhD, associate pathologist and director of Genitourinary Pathology Services at Mass General and the Mass General Cancer Center, and colleagues published the more recent results in Urologic Oncology.
As in the previous study, the subjects were 301 men who underwent in-office TBx with the PrecisionPoint Transperineal Access System (Perineologic, Cumberland, MD) between September 2019 and February 2021. All had at least one abnormal lesion (Prostate Imaging Reporting and Data System version 2 [PI-RADS] score ≥3) on prior prostate multiparametric MRI.
Prostate volume was classified as:
- Group A: ≤30 mL (20% of subjects)
- Group B: >30 to ≤45 mL (31%)
- Group C: >45 mL (49%)
Detection of clinically significant cancer was higher in group A than in the other groups with SBx, TBx, and the combination:
- SBx only—57% in group A, 35% in group B (P=0.026 vs. group A), and 34% in group C (P=0.008 vs. group A)
- TBx only—55% in group A, 43% in group B (similar to group A), and 28% in group C (P=0.001 vs. groups A and B)
- Combined—65% in group A, 54% in group B (similar to group A), and 40% in group C (P=0.008 vs. group A)
In group A, the figures for SBx alone, TBx alone, and the combined approach were statistically similar.
Six of the 39 cases of clinically significant prostate cancer in group A (15%) were missed by TBx but detected by SBx. Four of those six cases were present at the base location.
Additional Findings and Implications
TBx performance was similar across prostate volume groups in detecting the number of positive cores and the greatest percentage of cancer. This suggests TBx is a reliable biopsy strategy regardless of prostate volume.
MRI index lesion size was also similar across prostate volume groups, demonstrating MRI can accurately detect index lesions in smaller prostates. Enhancement of TBx precision can be expected when the index tumor size is similar but prostate volume is smaller.
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