The diagnostic value of MRI for persistent prostate cancer following irreversible electroporation focal therapy.

OBJECTIVE

To investigate the diagnostic value of magnetic resonance imaging (MRI) for persistent prostate cancer after irreversible electroporation (IRE) therapy.

PATIENTS AND METHODS

This is a post hoc analysis from a multicentre randomised trial, in which men with localised low- to intermediate-risk prostate cancer were randomised to receive either focal or extended IRE ablation. All patients underwent repeat MRI scans at 6 and 12 months and transperineal template mapping biopsy (TMB) at 6 months post-IRE. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of MRI were calculated for infield and outfield lesions using 2 × 2 contingency tables with 95% confidence intervals (CIs) for clinically significant prostate cancer and any-grade prostate cancer.

RESULTS

A total of 106 patients were recruited to this study, including 39 patients (37%) with clinically insignificant prostate cancer and 67 patients (63%) with clinically significant prostate cancer (International Society of Urological Pathology grade ≥2). Of these, 101 patients underwent repeat MRI scan and prostate biopsy at 6 months after IRE. The rate of clinically significant prostate cancer detected by TMB infield and outfield was 9.9% (10/101) and 9.9% (10/101), respectively. In the treated area, the sensitivity, specificity, PPV and NPV for MRI to detect clinically significant prostate cancer were 30% (95% CI 6.7%-65%), 91% (95% CI 82%-96%), 27% (95% CI 6.0%-61%) and 92% (95% CI 84%-97%), respectively. In the untreated area, the sensitivity, specificity, PPV and NPV of MRI to detect clinically significant prostate cancer were 20% (95% CI 2.5%-56%), 91% (95% CI 82%-96%), 20% (95% CI 2.5%-56%) and 91% (95% CI 82%-96%), respectively.

CONCLUSION

Favourable specificity but poor sensitivity was achieved with use of MRI to detect persistent clinically significant prostate cancer after IRE treatment. Repeat TMB should not be deferred, regardless of MRI results.