Cancer ablation with regional templates applied to prostatectomy specimens from men who were eligible for focal therapy

Abstract

Objective: To assess the totality of prostate cancer eradication in radical prostatectomy (RP) specimens from men with a unilaterally positive prostate biopsy, and who would currently qualify for subtotal prostate ablation with controlled thermal energy such as cryoablation or high-intensity focused ultrasound.

Materials and methods: Therapies for prostate cancer hold the promise of individualized treatment that selectively ablates the tumour while minimizing treatment-associated morbidity, but as prostate cancer is multifocal there are concerns about untreated residual disease. RP specimens (180) from men with a unilaterally positive prostate biopsy were examined to characterize the location, volume and grade of each tumour focus. Two treatment templates (hemiprostate and 'hockey-stick') were applied to every prostate cross-section. The nature of the in-field and out-of-field tumours was assessed and described for each treatment template.

Results: A single focus of cancer was the only tumour in 31 (17%) of the patients (contralateral cancer was present in 149, 83%, of specimens despite a unilateral positive biopsy). Hemiprostate and hockey-stick treatment templates covered all tumour foci in 17% and 47% of men, respectively. Most out-of-field cancers were clinically insignificant tumours not identified by prostate biopsy (low-volume, 0.5 mL; and low grade, Gleason score < or =6). Regional ablation would have successfully treated all clinically significant prostate tumours in 64% and 81% of patients using the hemiprostate or hockey-stick template, respectively. The hockey-stick template encompassed all dominant tumours (largest volume).

Conclusions: Regionally targeted prostate ablation is capable of eradicating all dominant tumours and the vast majority of clinically significant tumours in men with unilateral disease by biopsy. The study of focally ablative therapy should proceed under the auspices of an approved protocol.