Percutaneous transperineal radiofrequency ablation of prostate tumour: safety, feasibility and pathological effects on human prostate cancer

Abstract

To evaluate the safety of radiofrequency (RF) energy delivered interstitially in patients with prostate cancer scheduled for radical prostatectomy and to correlate the proposed theoretical lesion size with the pathological findings. Radiofrequency interstitial tumour ablation (RITA) was performed in 15 patients with localized prostate cancer before radical surgery. RF energy was delivered to the prostate by active needle electrodes (monopolar or bipolar) placed transperineally under transrectal ultrasonography guidance. Needle electrodes were used with different configurations and in some cases were covered by retractable shields to vary the length and circumference of the thermal lesions created. In eight patients, the procedure was performed immediately before radical prostatectomy, in six RITA was performed under spinal anaesthesia 1 week before surgery and in one patient, no surgery was performed but the patient was followed by serial determinations of prostate specific antigen (PSA). At least two lesions were created in each prostate, including both capsule and peripheral zones. NADPH and haematoxylin & eosin (H&E) staining were used to assess the extent of the necrotic lesion in the radical prostatectomy specimen. The mean energy delivered was 10.5 kJ, with central temperatures reaching up to 105 °C during 12 min of ablation; rectal temperature remained at <38 °C. There were no complications. Macroscopic examination showed well-demarcated lesions including the prostatic capsule, up to 2.2×1.5×4.5 cm. With monopolar energy, the observed lesion size was comparable to the predicted 2×2×2 cm lesion, while with bipolar energy, lesion size was related to interneedle distance and uncovered needle length. Microscopic examination showed clearly delineated lesions both with NADPH (in prostates immediately removed after surgery) and H&E (at 1 week after RITA) staining. The lesion size observed on pathological analysis correlated with the predicted lesion size. In one patient, no residual cancer was found in the specimen. In the patient whose entire prostate was targeted and followed by serial PSA measurements, the latter were undetectable at 3 months of follow-up. Transperineally delivered RF energy is capable of safely creating extensive coagulative necrotic lesions in prostate cancer tissue, in a reproducible and controlled manner. The results presented here provide basic information for the potential future application of this form of energy for localized prostate cancer.