eMedicine Specialties > Urology > Benign Prostatic Hypertrophy
Transurethral Microwave Thermotherapy of the Prostate (TUMT)
Updated: Feb 6, 2008
Introduction
Transurethral microwave thermotherapy (TUMT) is one of various procedures used for the treatment of lower urinary tract symptoms (LUTS) due to benign prostatic hypertrophy (BPH) in men. TUMT involves the insertion of a specially designed urinary catheter into the bladder, allowing a microwave antenna to be positioned within the prostate; there, it heats and destroys hyperplastic prostate tissue. The goal of TUMT is to provide a one-time efficacious treatment of LUTS due to BPH as an alternative to pharmacotherapy, transurethral resection of the prostate (TURP), transurethral needle ablation (TUNA), photoselective vaporization of the prostate (PVP), open prostatic enucleation, or other surgical therapies.
History of the Procedure
McCaskey used heat in the form of ultraviolet lamps to treat prostatism in 1921. In 1929, Corbus used diathermy probes for the same purpose. Yerushalmi and associates reintroduced microwave therapy for prostatic enlargement in 1985 using a transrectal probe to treat patients with BPH who were otherwise poor operative candidates.1
The first TUMT clinical trials used a transurethral catheter in a series of ten 1-hour sessions, although the software and instrumentation allowed only a limited and often interrupted delivery of energy to the prostate. Intraprostatic temperatures reached 40-45°C, and symptomatic improvement was suggested to be due to destruction of the alpha-adrenergic nerve fibers around the prostate, as an objective improvement of voiding parameters was not observed and histologic studies revealed that prostatic cells were not destroyed.
It has since been shown that prostate cells are not reliably destroyed until temperatures reach 45°C (113°F). The term thermotherapy was therefore coined to describe treatment temperatures above 45°C and hyperthermia for those below this level. However, urethral-pain threshold was shown to be 45°C (113°F); therefore, higher energy and higher temperatures were achieved only with the introduction of urethral cooling during therapy.
Improvement in antennae design allowed better distribution of the energy to the transition zone of the prostate, the main source of adenomatous tissue. With thermotherapy, both objective and subjective parameters reflected significant improvement. Histologic examination of specimens revealed cell destruction but no reliable cavitation. Patients invariably had severe prostatic edema and urinary retention, requiring the use of a urinary catheter.
High-energy thermotherapy has since been introduced; it can achieve temperatures greater than 70°C (158°F), causing thermoablation of prostatic tissue. Unlike thermotherapy, high-energy thermoablation caused prostatic cavities, resulting in greater improvement in symptoms and objective parameters. However, unlike with TURP, patients did not notice an immediate improvement but, rather, a gradual change over a period of months.
Problem
BPH is one of the most common diseases in aging men. An estimated one third of men older than 50 years develop LUTS, and 30% of these men eventually require surgery. Irritative voiding symptoms, such as frequency, urgency, urge incontinence, and nocturia, severely affect patients' quality of life and perception of health. If left untreated, bladder outlet obstruction could lead to urinary stasis, predisposing patients to urinary tract infections and urosepsis, bladder dysfunction, bladder calculi, and renal failure.
Frequency
Adenomatous prostatic growth is believed to begin at approximately age 30 years. An estimated 50% of men have histologic evidence of BPH by age 50 years and 75% by age 80 years. In 40-50% of these patients, BPH becomes clinically significant.
Etiology
The normal prostate is composed of a combination of glandular, stromal, and smooth muscle cells. BPH is due to a proliferation of glandular elements, fibromuscular (stromal) elements, or both. Unlike prostate cancer, which invariably originates in the peripheral zone of the prostate, BPH occurs in the transitional zone and the periurethral area.
The hyperplastic growth of prostate tissue is believed to be due, at least in part, to stimulation by dihydroxytestosterone (DHT), which is converted from testosterone by the action of 5-alpha reductase within the prostate. The only known risk factors for BPH are aging and intact testes.
Pathophysiology
BPH is a nodular regional growth with a variegated gross appearance. Nodules of varying sizes may appear anywhere in the prostate, although more commonly in the transitional zone and periurethral areas. The prostatic capsule acts somewhat as a barrier to outward growth, so, as nodules grow, they may compress the urethral lumen. No correlation exists between the size of the prostate or prostatic nodules and urethral occlusion.
As urethral resistance to urinary flow increases, the bladder is initially able to maintain urinary flow parameters via detrusor muscle hypertrophy. Uncorrected, this initial adaptation leads to the replacement of the smooth muscle cells with collagen, resulting in decreased bladder compliance and, eventually, detrusor failure.
Presentation
The clinical presentation of patients with LUTS is varied. Patients may present with storage symptoms such as nocturia, urinary frequency, urgency, or dysuria. Obstructive symptoms such as a weak urinary stream, double voiding, hesitancy, and a feeling of incomplete emptying are more common when the bladder compensation is compromised. Others may present with urinary tract infections, bladder stones, abdominal pain, or even renal failure. In these situations, the kidneys should be evaluated for hydronephrosis. Patients with microscopic or gross hematuria must be evaluated for urothelial, prostatic, or renal neoplasms.
All patients considered for TUMT require a thorough history and physical examination. The history of present illness should include the presence, onset, progression, and severity of LUTS. The past medical history should include the patient's urologic history (including sexually transmitted diseases, stones, trauma, and bladder function) along with other concomitant medical problems (eg, diabetes). Medicines containing alpha sympathomimetics, such over-the-counter cold remedies, may cause symptoms of bladder outlet obstruction and should be withheld when possible. A family history should focus on a history of urologic cancer, and a social history should focus on risks for cancer such as a smoking history and occupational exposure.
The physical examination should be systematic and meticulous. The patient should be evaluated specifically for distended bladder, urethral meatal stenosis, and nodularity. Variables such as rectal tone, prostatic size, consistency, and landmarks should also be assessed.
Indications
Candidates for transurethral microwave thermotherapy (TUMT) include persons with moderate-to-severe voiding symptoms due to benign prostatic hypertrophy (BPH), those with side effects to medical therapy, those in whom medical therapy has failed, and those who choose to not be treated medically.
Relevant Anatomy
The urinary bladder is derived embryologically from the urogenital sinus. Parasympathetic nerves stimulate the detrusor musculature of the bladder to contract, while alpha-adrenergic nerves from the pelvic plexus cause contraction and increased bladder outlet resistance in the prostatic stroma, capsule, bladder neck, and periurethral area. The prostate, which originates from the mesenchyme surrounding the urogenital sinus, is a compound tubuloalveolar gland whose base abuts the bladder neck and whose apex merges with the membranous urethra at the urogenital diaphragm. The normal adult gland is cone-shaped and has a mean size of 4.4 cm transverse, 2.6 cm anteroposterior, and 3.4 cm in length. The prostate can be divided into zones, with one of the more common classifications based on studies by McNeal, who describes anterior, peripheral, transitional, and central zones.
Contraindications
Active urinary infection is a contraindication to urethral instrumentation. Patients should be evaluated for prostate or urothelial cancer when necessary and treated appropriately. Those with neurogenic voiding dysfunction must also be treated appropriately.
Patients with a history of TURP or severe pelvic trauma should not undergo transurethral microwave thermotherapy (TUMT) because of potential alterations in pelvic anatomy.
Patients with glands smaller than 30 g or a prostatic urethral length of less than 3 cm respond poorly to TUMT, as do patients with glands larger than 100 g and patients with a prominent median bar.
Patients with metallic implants, penile prostheses, artificial urinary sphincters, severe urethral stricture disease that prohibits proper probe placement, severe peripheral vascular disease with claudication, or Leriche syndrome should not undergo TUMT. Patients with a significantly decreased pain response should be approached with caution.
Patients who desire future fertility should be cautioned about the potential risk for postoperative retrograde ejaculation and erectile dysfunction.
Patients with pacemakers need clearance from their cardiologists; pacemakers may need to be turned off during therapy. Regardless, performing TUMT in this group should be approached with apprehension.
Hip replacement is no longer a contraindication to TUMT. Acute urinary retention was once thought to be a contraindication to TUMT; however, high-energy TUMT has shown promising initial results in select patients.
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Keywords
transurethral microwave thermotherapy of the prostate, TUMT, hyperthermia, thermotherapy, thermoablation, benign prostatic hypertrophy, microwave therapy, prostatism, lower urinary tract symptoms, LUTS, BPH, transurethral resection of the prostate, TURP, Targis system, Targis machine, Prostasoft 2.0, Prostasoft 2.5, Prostasoft 3.5, open prostatic enucleation, open prostatectomy, adenomatous hyperplasia, nocturia, urinary frequency, urgency, dysuria, urinary tract infection, bladder stones, renal failure, hydronephrosis, microscopic hematuria, gross hematuria, neurogenic voiding dysfunction, urethral stricture, prostatitis, urinary bladder, high-energy transurethral microwave thermotherapy of the prostate, high-energy TUMT
