Ferromagnetic thermal ablation of locally recurrent prostate cancer: prostate specific antigen results and immediate/intermediate morbidities.

Abstract

Curative options for locally recurrent prostate cancer following external beam radiotherapy are limited due to the significant morbidity associated with surgical therapy. ThermoRods (Ablation Technologies, San Diego, California) are permanently implantable, 14 mm cobalt-palladium alloy rods that produce heat through oscillation of a magnetic field. The rod is designed to self-regulate the temperature to 70C by a temperature dependent magnetic transition (Curie effect). We determined whether patients with prostate cancer and local failure could be treated with thermal ablation of the prostate using this novel technology. A total of 14 men with an average age of 72 years (range 62 to 81) were enrolled in the study. All had biopsy proven prostate cancer with increasing prostate specific antigen (PSA) (1.0 to 10.3 ng/ml). The seminal vesicles were not routinely biopsied. Metastatic disease was assayed in all men with bone scan and in later patients with abdominopelvic computerized tomography. Patients had ThermoRods placed under transrectal ultrasound guidance, similar to brachytherapy. The pre-plan was rigorously followed to produce a 3-dimensional array with rods separated by 1 cm across the short axis. Patients were treated in a magnetic field for 1 hour. Urethral and rectal temperatures were also monitored and cooled appropriately. Serial PSA measurements and 6 month posttreatment biopsies were obtained after the procedure. Average time since radiation was 4.5 years. PSA nadir values after radiation were between 0.3 and 2.2 ng/ml. Prostatic temperatures were homogeneously increased greater than 50C, while rectal and urethral temperatures did not exceed 44C at any point. The urethral catheter was removed 2 weeks postoperatively in all cases. Six months after the procedure 8 of the 14 men (57%) had a PSA decrease to less than 0.1 ng/ml. Complications included urinary retention as well as incontinence. Incontinence was generally temporary and only 1 patient (7%) had long-term incontinence. Most patients were impotent after treatment. Of the patients 21% experienced urinary retention. Five patients (36%) needed to undergo secondary procedures after therapy, including transurethral prostate resection in 2, balloon dilation in 1, cystoscopic removal of necrotic tissue in 1 and bladder irrigation in 1. This novel means of thermal ablation produces significant PSA decreases in patients. Morbidity is predominantly in the form of incontinence and impotence. Incontinence is generally temporary. The use of ferromagnetic rods enables the precise control of tissue destruction with the sparing of immediately adjacent structures. The technology uses skills familiar to the urologist and avoids radiation. The durability of the PSA response and incidence of late morbidity remain to be defined.