Focal Ablative Therapy for Prostate Cancer: What You Need to Know

Andrew Siegel MD  10/19/19

As an alternative to reading this blog, if you would prefer the audio version read by yours truly, click here: audio version of focal ablative therapy

There are alternatives to radical prostatectomy and radiation therapy as treatment for prostate cancer.  Focal ablative therapies use different forms of energy—heating, freezing, etc.— to target and destroy defined portions of the prostate gland. Focal ablative therapies require precise imaging and pathological mapping of the prostate cancer, facilitated by the increasing popularity of MRI-guided biopsies. Focal ablation is best considered for low risk or low-volume intermediate risk cancer, whereas whole gland treatment is better for high risk or high-volume intermediate risk prostate cancer. Optimal candidates for focal therapy have a single MRI detectable lesion that correlates with pathological T1c-T2a Gleason 3+3 or 3+4 cancer, PSA < 15, and a life expectancy > 10 years.

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Fire and Ice;  Thank you Michele Bettuolo and Pixabay for image above

 

“Focal” refers to treating only the region of concern, sparing the remainder of the prostate.  “Ablative” refers to the destruction of tissue.  The challenge is that prostate cancer is often multifocal, with disease present in multiple areas and involving both sides of the prostate. Focal therapies are based on the theory that although prostate cancer is usually multifocal, there is often a single “index” area that contains the most aggressive, at-risk disease, which is the region targeted.  Quality imaging and mapping biopsies of the prostate are essential in order to determine the precise location of the index area. A problem with MRI is that it can underestimate the size of the index area and can miss some clinically significant cancers. Focal therapies, although theoretically advantageous in sparing portions of the prostate, pose the risk of leaving cancer untreated.  Focal ablation can potentially serve as a “bridging” therapy between the extremes of active surveillance and active treatment (surgery or radiotherapy).

When ablative therapies are used to treat the entire prostate gland, significant side effects often occur.  These include a prolonged need for a urinary drainage catheter, bothersome lower urinary tract symptoms, sloughing (passage of dead tissue through the urethra), urethral scarring and sexual issues. These side effects are less of a concern when ablative therapy is directed focally at only the region of concern.

Cryosurgery, a.k.a. cryotherapy or cryoablation, freezes prostate cancer cells. Prostate “frostbite” disrupts the cell membranes and the blood supply of prostate cancer cells, resulting in the destruction of the frozen tissue. As it is challenging to achieve uniform cold temperatures throughout larger prostate glands, prostate size is an important factor in selecting patients who are appropriate for this means of treatment. Cryosurgery incurs a very high risk of erectile dysfunction.

Freezing is achieved using cryoprobes that are positioned strategically within the prostate gland (similarly to how needles are placed into the prostate for brachytherapy radiation) using ultrasound guidance via a probe placed in the rectum and a perineal template. Pressurized argon gas is the medium used to freeze tissue. The procedure is performed under anesthesia with legs up in stirrups.  To avoid damaging the urethra, it is warmed with a warming catheter that uses helium gas. Devices called thermocouples precisely monitor temperatures. A tissue temperature of –40 to –50 degrees Centigrade is achieved. Under most circumstances, the prostate is subjected to two cycles of freezing and thawing. The procedure can usually be done on an outpatient basis, with the patient sent home with a catheter for 1-3 weeks.

“Primary” cryosurgery is most effective for men with localized low and intermediate risk prostate cancer who are not suitable candidates for prostatectomy or radiation therapy and are not sexually functional nor interested in being sexually active. If the prostate is large, androgen deprivation therapy is useful to reduce the prostate volume and allow for more effective results. Freezing extending beyond the capsule of the prostate can potentially treat extra-capsular disease. “Salvage” cryosurgery is used for recurrent prostate cancer following radiation therapy.

Cryosurgery is still considered by many to be an emerging therapy and not quite in the same league as prostatectomy and radiotherapy.  However, technological improvements in hardware and software have substantially improved the current generation of cryosurgery as compared to previous iterations.

Advantages of Cryosurgery:

  • Outpatient procedure with minimal time lost from normal activities
  • Relatively non-invasive
  • Can be repeated if necessary
  • Can target prostate cancer while sparing uninvolved areas of the prostate

Disadvantages of Cryosurgery:

  • Attempted targeted treatment of cancer may unknowingly leave behind cancerous prostate tissue
  • Need for prolonged bladder catheterization
  • Potential damage to the urethra and rectum resulting in a recto-urethral fistula, an abnormal connection between these two structures, especially after salvage cryosurgery
  • Urethral sloughing (passage of dead tissue through the urethra) resulting in urethral scarring and urinary difficulties, which occurs more commonly in men who have had previous procedures for benign prostate enlargement
  • Pelvic pain (usually short term)
  • Urinary issues including obstructive and irritative lower urinary tract symptoms and incontinence
  • Erectile dysfunction is an expected outcome
  • Rare pubic bone osteomyelitis (bone infection), especially after salvage cryosurgery

High-intensity focused ultrasound (HIFU) is a minimally invasive, alternative means of treating localized prostate cancer using thermal energy. It was approved by the FDA in 2015, although it has been available since 1995. Over the years, there have been numerous advances in both the HIFU software and hardware. Currently there are two main systems in use in the United States, the Ablatherm and the Sonablate.

Under anesthesia, a probe that generates high-intensity ultrasound waves is placed in the rectum. HIFU waves are delivered to the target area within the prostate to destroy cancer cells by means of heat destruction, without damaging tissue in the ultrasound beam pathway. A rectal cooling system is utilized to protect the rectum.

Overlapping target areas are defined and treated over the course of the 1-4 hours that it takes to do the procedure. Similar to cryosurgery, HIFU can be used either as “primary” therapy or alternatively as “salvage” therapy for recurrent prostate cancer following radiation failure. It can be used focally, to ablate half the prostate or to ablate the total prostate gland.

In addition to the thermal effect (heating tissue up to 85 degrees Centigrade), HIFU also functions via a mechanical effect (prostate cancer cell wall rupture) and a tissue effect (prostate cancer cell death and scarring).

If necessary, trans-urethral resection of the prostate (a procedure to create a channel through the prostate gland), is performed prior to HIFU to reduce the size of the prostate and minimize the possibility of urinary difficulties after the procedure, since urinary obstruction due to scarring and prostatic tissue sloughing are the most common side effects. A catheter is generally required for 3-7 days following the procedure.

Numerous long-term studies with over 10-year follow-up from Europe have shown cancer-free status equivalent to surgery or radiation. Since FDA approval, HIFU is considered by many as an attractive procedure, especially for less aggressive, relatively favorable or low volume disease. HIFU provides a better chance of preserving sexual function as compared to surgery or cryotherapy. A major challenge is the fact that many insurance companies do not yet pay for HIFU.  At the current time, Medicare covers the HIFU facility fee, but not the professional fee.  Most commercial insurances do not cover HIFU, although some cover salvage HIFU and some provide coverage on a case-to-case basis.

Advantages of HIFU:

  • Outpatient, non-invasive procedure with little time lost from normal activities
  • Minimal side effects, especially with targeted therapy
  • Can be repeated if necessary
  • Can target prostate cancer while sparing uninvolved areas of the prostate
  • Better odds at preserving erections

Disadvantages of HIFU:

  • Difficulty in treating the entire prostate when prostate is very large (although second generation device has a much greater reach)
  • Attempted targeted treatment of cancer may unknowingly leave behind cancerous prostate tissue
  • Requirement for general anesthesia
  • Heat damage of nerves causing erectile dysfunction in approximately 30% of patients undergoing full gland treatment
  • Rare recto-urethral fistula, especially after salvage HIFU
  • Rare pubic bone osteomyelitis (bone infection), especially after salvage HIFU

 Additional focal therapies under investigation

As of now, these forms of focal ablation are investigational and experimental. Clinical trials are limited by short-term follow up and it will take a number of years to accrue the data necessary to gauge their success.

 MRI-guided focal laser ablation uses MRI to image and identify the cancerous region of concern. A laser fiber is guided into the interior of this selected region and laser energy is used to focally destroy it.

Irreversible electroporation uses pulsed, low-energy direct current to create micropores in cell membranes that lead to their rupture and destruction.

Vascular targeted photodynamic therapy ablates the tissue of concern via trans-perineal or trans-rectal laser activation of an intravenously given vascular photosensitizer.  By exposure to a certain wavelength of light, the light-activated photosensitizer produces free radicals that cause the focal ablation.

Bottom Line: Focal ablative therapies are emerging options that show promise in terms of short-term cancer results and a relatively favorable side effect profile, but they require further evaluation, clinical trials and follow up to assess their long-term cancer outcomes.

Wishing you the best of health,

2014-04-23 20:16:29

A new blog is posted weekly. To receive a free subscription with delivery to your email inbox visit the following link and click on “email subscription”:  www.HealthDoc13.WordPress.com

Dr. Andrew Siegel is a physician and urological surgeon who is board-certified in urology as well as in female pelvic medicine and reconstructive surgery.  He is an Assistant Clinical Professor of Surgery at the Rutgers-New Jersey Medical School and is a Castle Connolly Top Doctor New York Metro Area, Inside Jersey Top Doctor and Inside Jersey Top Doctor for Women’s Health. His mission is to “bridge the gap” between the public and the medical community. He is a urologist at New Jersey Urology, the largest urology practice in the United States.

The content of this entry is excerpted from his new book, PROSTATE CANCER 20/20: A Practical Guide to Understanding Management Options for Patients and Their Families

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Video trailer for Prostate Cancer 20/20

Preview of Prostate Cancer 20/20

Andrew Siegel MD Amazon author page

Prostate Cancer 20/20 on Apple iBooks

PROSTATE CANCER 20/20: A Practical Guide to Understanding Management Options for Patients and Their Families is now on sale at Audible, iTunes and Amazon as an audiobook read by the author (just over 6 hours). 

Dr. Siegel’s other books:

FINDING YOUR OWN FOUNTAIN OF YOUTH: The Essential Guide to Maximizing Health, Wellness, Fitness and Longevity

PROMISCUOUS EATING— Understanding and Ending Our Self-Destructive Relationship with Food

MALE PELVIC FITNESS: Optimizing Sexual and Urinary Health

THE KEGEL FIX: Recharging Female Pelvic, Sexual, and Urinary Health

 

 

 

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