What is focal therapy for localized prostate cancer?

Localized prostate cancer is cancer that has spread (metastasized) no farther than the tissue surrounding the prostate gland. Focal therapy is a treatment for this type of prostate cancer.

For many years there have been two main approaches to treating localized prostate cancer. The first is active surveillance or “watchful waiting.” In cases of older men or low-risk patients, regular medical tests are conducted to make sure the cancer is not spreading. No other action is taken because the cancer is stable or growing so slowly it will not cause problems any time soon. If tests show the cancer is spreading, treatments can begin. Of those men assigned to active surveillance, 14% to 41% will eventually require surgery or radiation.

The second approach to treating localized prostate cancer has been the use of radiation or surgery. This is effective for removing any tumors present but often causes negative side effects in the urinary, genital, or rectal areas. Two common side effects include loss of control over urinary functions (incontinence), and impotence (the inability to maintain an erection).

Focal therapy offers a middle-ground treatment. The idea behind focal therapy is to reduce the amount of damage to the prostate gland and surrounding areas while still treating the cancer effectively.

This is done by focusing treatment on what is known as the index lesion, which is usually defined as the largest tumor with the highest grade. The grade, or Gleason score, is determined by looking at cancer cells under a microscope to see how fast the disease is spreading.

Even though many cases of prostate cancer have more than one tumor site, some researchers believe that the index lesion is what drives and predicts how any particular cancer will progress. If growth of the index lesion can be controlled with focal therapy, the thought is that the cancer as a whole can be managed with fewer bad side effects.

What treatments are used in focal therapy for localized prostate cancer?

Focal therapy uses ablation, which is the use of extreme temperatures to destroy tumors. In focal ablation, the area of the prostate that contains the most serious cancer is targeted, rather than treating the entire prostate gland. Focal ablation techniques include:

  • Cryotherapy: Use of very cold gases passed through needles to freeze and destroy cancer tissue.
  • HIFU (High Intensity Focused Ultrasound): The use of high-frequency sound waves directed at the tumor through an ultrasound probe inserted into the rectum. The high intensity waves cause the diseased tissue to heat up and die.
  • Photodynamic therapy: A drug called a photosensitizer is injected into the bloodstream. This drug then absorbs light rays directed at the tumor, and produces an active form of oxygen that destroys cancer cells.
  • Laser ablation: The use of laser radiation energy pinpointed to a very small area to burn away cancerous tissue. Laser ablation has the advantage of being able to be performed at the same time as magnetic resonance imaging (MRI), allowing very specific targeting and also real-time views of results.

Who are good candidates for focal therapy?

When focal therapy for prostate cancer first began to be used in about 2007, it was only as an alternative to active surveillance in very low-risk patients. Since then, the use of focal therapy has expanded to include some intermediate- and even high-risk patients.

Although there are no set rules about which patients make the best candidates for focal therapy, those with overall low or intermediate risk, and who have biopsy-proven cancer located in only one area, are usually the best choices for this type of treatment.

In each case, the doctor will consider the patient’s general health and mental outlook, the size and location of the tumors present, and their chances of spreading more. Use of tests such as MRI, ultrasound, and biopsy (tissue samples examined in the laboratory) can help decide if a patient will benefit more from focal therapy or from traditional treatments.

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