Magnetic resonance imaging targeted biopsy in biopsy-naïve patients and the risk of overtreatment in prostate cancer: a grading issue

Early experience with targeted and combination biopsies in prostate cancer work-up in Denmark from 2012 to 2016

PURPOSE

To investigate the early implementation of combined systematic and targeted (cBx) primary biopsy in prostate cancer diagnosis and define the concordance in Gleason grading (GG) of different biopsy techniques with radical prostatectomy (RP) pathology.

METHODS

This population-based analysis includes data on all men in Denmark who underwent primary cBx or standalone systematic (sBx) prostate biopsy between 2012 and 2016. Biopsy results were compared to RP pathology if performed within a year. Concordance measurement was estimated using Cohen's Kappa, and the cumulative incidence of cancer-specific death was estimated at 6 years with the Aalen-Johansen estimator.

RESULTS

Concordance between biopsy and RP pathology was 0.53 (95CI: 0.43-0.63), 0.38 (95CI: 0.29-0.48), and 0.16 (95CI: 0.11-0.21) for cBx, targeted biopsy (tBx), and sBx, respectively. For standalone sBx and RP, concordance was 0.29 (95CI: 0.27-0.32). Interrelated GG concordance between tBx and sBx was 0.67 (95CI: 0.62-0.71) in cBx. The proportion of correctly assessed GG based on RP pathology was 54% in both cBx and standalone sBx. Incidence of prostate cancer-specific death was 0% regardless of biopsy technique in GG 1, and 22% (95CI: 11-32), 30% (95CI: 15-44), and 19% (95CI: 7.0-30) in GG 5 for cBx, tBx, or sBx, respectively.

CONCLUSION

Overall, the cBx strategy demonstrates higher concordance to RP pathology than the standalone sBx. However, cBx exhibits more overgrading of the GG of RP pathology compared to sBx. Ultimately, the classic grading system does not take change in the diagnostic pathway into account, and grading should be altered accordingly to ensure appropriate treatment.