Microwave thermotherapy: historical overview

In vivo temperature mapping of prostate during treatment with TherMatrx TMx-2000 device: heat field and MRI determinations of necrotic lesions

BACKGROUND AND PURPOSE

The effectiveness of any thermotherapy device is determined by the temperatures created and how long they are applied. Understanding the heating characteristics of a thermotherapy device is vital to its correct implementation. Interstitial temperature mapping was used to determine the heat field created within the prostate by the TherMatrx TMx-2000 transurethral microwave thermotherapy (TUMT) device. Gadolinium-enhanced MRI was used to determine the extent, type, and pattern of coagulation necrosis caused by TUMT.

PATIENTS AND METHODS

Interstitial temperature mapping was performed during treatment in five patients with benign prostatic hyperplasia using 24 temperature sensors inserted through the perineum and arrayed throughout the prostate under ultrasound and X-ray guidance. Gadolinium-enhanced MRI scans were performed on all patients 1 week after treatment.

RESULTS

Interstitial temperature mapping found the heat field created to peak at the urethral surface near the central part of the catheter antenna. Temperatures decreased at consistent rates of 1 to 1.4 degrees C/mm radially and 0.1 to 0.5 degrees C/mm longitudinally from the peak area. Gadolinium-enhanced MRI showed minimal dispersed necrosis and only in the periurethral area.

CONCLUSIONS

The TMx-2000 can create temperatures >45 degrees C in areas 3 to 4 mm from the antenna. However, the heat pattern and protocol of the TMx-2000 produce necrosis-generating conditions only within a few millimeters of the urethra.

Efficacy of high-energy transurethral microwave thermotherapy in alleviating medically refractory urinary retention due to benign prostatic hyperplasia

OBJECTIVES

To determine the efficacy of high-energy transurethral microwave thermotherapy (HE-TUMT) in treating patients with medically refractory complete urinary retention secondary to benign prostatic hyperplasia (BPH).

METHODS

Between April 2000 and July 2003, 39 patients in urinary retention due to BPH were treated with HE-TUMT. A Foley catheter was reinserted after HE-TUMT and removed at 3 weeks for a voiding trial. Patients unable to void were recatheterized, and voiding trials were repeated at 2-week intervals. Patients were evaluated according to history and physical examination, prostate-specific antigen level, prostate volume, cystourethroscopy, International Prostate Symptom Score, quality of life score, peak uroflow, and postvoid residual. Success was defined as the ability to urinate after HE-TUMT without the need for further intervention.

RESULTS

The mean (+/- SD) patient age was 72 +/- 9.3 years. Mean follow-up period was 18 +/- 10.2 months. Twenty patients (51%) were characterized as American Society of Anesthesiologists class III or higher. The mean prostate volume was 75.2 +/- 57.6 cm3. The mean length of time that patients were dependent on indwelling Foley catheters before HE-TUMT was 9.6 +/- 14.2 weeks. Thirty-two patients were able to void after HE-TUMT, for an overall success rate of 82%. Patients voiding successfully after HE-TUMT had a mean of 1.6 +/- 0.8 voiding trials and required catheters after HE-TUMT for a mean period of 4.1 +/- 2 weeks. Only 6 (15%) of the patients who were voiding were able to stop their medication for BPH.

CONCLUSIONS

We found an encouraging success rate with HE-TUMT in relieving urinary retention in patients with BPH, including those with large prostate volumes. It is an acceptable option for patients who are considered high risk for surgery. Several patients required multiple voiding trials before spontaneous urination, which suggests that improvements in bladder outlet obstruction might require a prolonged period after HE-TUMT. Finally, many patients might require continued use of medications after HE-TUMT.

Long-term treatment outcomes of CoreTherm microwave feedback thermotherapy

The gold standard for definitive management of symptomatic benign prostatic hypertrophy is transurethral resection of the prostate (TURP). Despite its efficacy, TURP has significant morbidity/mortality concerns such as hemorrhage and transurethral resection syndrome. This is especially worrisome for the medically high-risk patient, but the high rates of retrograde ejaculation found with TURP also pose a problem for young patients. A minimally invasive, outpatient alternative to TURP that has long-term efficacy, low morbidity/mortality, and provides a cost-effective advantage is in high demand. This review article discusses microwave thermotherapy as such an option and reports the long-term experience with the CoreTherm (CoreTherm Operations AB, Sweden) device.

Application of External Microwave Thermotherapy in Urology: Past, Present, and Future

The excellent clinical results of transurethral microwave thermotherapy (TUMT) for the treatment of symptomatic benign prostatic hyperplasia (BPH) gave to TUMT the leading position among the microwave thermotherapy modalities available for the treatment of different urologic conditions. Research in TUMT has focused on operating software, temperature monitoring, intraprostatic heat distribution, cell-kill calculations, and correlations with clinical variables. Randomized comparisons of TUMT with other established therapies for BPH, including transurethral resection, have facilitated the evaluation of the clinical outcome, durability, morbidity, and costs of the treatment. The applications of microwave thermotherapy in other urologic diseases are also presented in this review.

Transurethral microwave thermotherapy: the gold standard for minimally invasive therapies for patients with benign prostatic hyperplasia?

From all available minimally invasive methods for the treatment of symptomatic benign prostatic hyperplasia (BPH), transurethral microwave thermotherapy (TUMT) has gained a firm position as the most attractive option. Recent research has produced innovations in high-energy TUMT, including new treatment protocols, refined selection criteria, and monitoring of intraprostatic temperature. Furthermore, long-term results from randomized studies comparing TUMT with transurethral resection of the prostate (TURP) or medical treatment are now available. All these data indicate that more durable clinical outcomes and less morbidity can be achieved with TUMT, strengthening its position as a standard treatment for BPH. This paper describes the status of TUMT in the treatment of lower urinary tract symptoms related to BPH, focusing on variations in the outcomes with different devices, the durability of treatment outcomes, morbidity, selection criteria, and cost. The relation of TUMT to medical management and TURP also is addressed.

Thermotherapy and thermoablation for benign prostatic hyperplasia

PURPOSE OF REVIEW

From all the available thermoablative methods for the treatment of symptomatic benign prostatic hyperplasia, transurethral microwave thermotherapy is considered as standard in minimally invasive management. The literature is enriched by several new studies on transurethral microwave thermotherapy, and thus this review presents up-to-date information about thermotherapy.

RECENT FINDINGS

New studies have provided significant information regarding differences in outcome for devices with different protocols and selection criteria, confirming the superiority of high-energy programmes. Furthermore, monitoring of the intraprostatic temperature promises better clinical results by means of individualization of the treatment. Long-term results have been available and allow the evaluation of the fundamental issue of treatment durability. Improvement after high-energy transurethral microwave thermotherapy remains durable for more than 2.5 years. Randomized studies comparing this treatment with other established therapies for benign prostatic hyperplasia, including medical treatment and transurethral resection of the prostate, have also contributed to an evaluation of the morbidity, and costs of treatment. Clinical outcomes with transurethral microwave thermotherapy are in the range of those obtained with transurethral resection of the prostate and are superior to those of medical management. Retreatment after transurethral resection of the prostate emerges because of complications following the procedure, whereas retreatment after transurethral microwave thermotherapy is as a result of treatment failure. In addition, the rate of failure of medical management is almost seven times higher than that for transurethral microwave thermotherapy. Thus, the latter seems to play a dominant role in the economic models used to assess the cost-efficiency of different treatment modalities for benign prostatic hyperplasia.

SUMMARY

The recent innovations in high-energy transurethral microwave thermotherapy provide better and more durable clinical outcomes and lower morbidity, and strengthen its position as an established treatment for benign prostatic hyperplasia. However, there is always room for improvement, so further research on therapeutic protocols, treatment monitoring and selection criteria are to be welcomed.