Determination of the Optimal Targeted Prostate Biopsy Strategy




Subramanian, Naveen Gopal

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BACKGROUND: Prostate cancer is one of the leading causes of cancer-related mortality in men and is treated in different ways based on the aggressiveness of the disease. The traditional method of diagnosis has been the systematic biopsy, which frequently underestimates or completely misses the disease. Recently, targeted prostate biopsies using pre-biopsy multiparametric MRI (mpMRI) have increased the detection of clinically significant disease. Of these methods, the two most sophisticated types are the MRI-TRUS fusion biopsy and the direct in-bore biopsy. Data comparing the diagnostic accuracy of these approaches and optimization of the biopsy procedure are lacking. OBJECTIVE: To compare the diagnostic accuracy of in-bore biopsy and MRI-TRUS fusion biopsy at accurately determining the index lesion grade group compared to radical prostatectomy (Aim 1), and to establish the optimal number of cores taken during in-bore biopsies to maximize detection of clinically significant disease while minimizing duration of the biopsy (Aim 2). METHODS: In Aim 1, patients that had at least one prostate lesion with abnormal mpMRI (at least one PI-RADS score 3 lesion) followed by targeted biopsy between April 2017 and January 2019 were included. The decision of what biopsy method to use for each patient was made by the ordering provider. The index lesion was defined as the largest lesion that exhibited the highest grade group (GG) and/or stage. The reference standard was the highest GG obtained from the radical prostatectomy specimen. In Aim 2, patients with abnormal mpMRI followed by in-bore biopsy between May 2017 and December 2019 were included. The endpoints of the study were the detection rate of clinically significant disease (defined as a GG of at least 2) and the GG upgrade (defined as the increase in the cumulative maximum GG with each additional core). RESULTS: In Aim 1, there was a statistically significant difference in the number of GG upgrades between the two biopsy types, with the in-bore biopsy having fewer (14%) upgrades than the fusion biopsy (30%; p=0.012). The mean net GG change was also significantly lower in the in-bore cohort (-0.11) compared to the fusion cohort (+0.16; p=0.0085). The GG concordance of the in-bore cohort (61%) was higher than the fusion cohort (53%) when compared to radical prostatectomy. In Aim 2, clinically significant cancers were detected by the first biopsy core in 78% of cases, the second core in 13% of cases, and the third core in 8.1% of cases. Only two lesions had the fourth core find csPCa. GG upgrade from insignificant to significant disease was also higher in the second and third cores (3%) compared to the fourth and fifth cores. The fourth and fifth cores only detected 0.3% of clinically significant tumors and resulted in only 1.2% of GG upgrades. CONCLUSION: Direct in-bore MRI-guided biopsy has greater diagnostic accuracy and a lower incidence of GG upgrades compared to MRI-TRUS fusion biopsy. Three cores per lesion was determined to offer the optimal balance between increasing the detection of clinically significant cancers and minimizing biopsy duration. Future work will center around cost-effective analyses and the impact on long-term patient outcomes.

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