What is focal therapy of prostate cancer?

Focal therapy is an individualized approach to prostate cancer treatment that aims to destroy areas of known cancer while preserving uninvolved, non-cancerous tissue, and therefore, preserve quality of life by reducing the side effects (impotence, incontinence) commonly seen with conventional whole gland therapies (eg. surgery, radiation therapy).

Duke is a leading center for the study of focal therapy for prostate cancer. Many centers and organizations consider focal therapy to be an investigational treatment option.

There are different types of focal therapy:

• Unifocal/multifocal therapy (figure A): Selective treatment of the identified prostate cancer lesions (red area)
• Hemiablation (figure B): Destruction of one-half of the prostate gland involved with cancer (red area) and leaving unharmed the contralateral, non-cancerous portion
• Extended ablation (figure C): Hemiablation with extension of tissue destruction to portions of the contralateral side
• Subtotal ablation (figure D): Destruction of almost all prostate tissue on both sides preserving the neurovascular bundle (yellow area) on one side

Four types of focal therapy
(Click image to enlarge.)

Who is a candidate for focal therapy?

Not all patients with prostate cancer are ideal candidates for focal therapy. However, about 20 percent of men diagnosed with prostate cancer may benefit from this treatment.

Potential candidates include patients with early stage, localized disease with favorable characteristics in terms of PSA, digital rectal examination, and biopsy results (low Gleason score, minimal number of cores with cancer).

Currently, the most used approach for focal therapy is hemiablation, meaning destroying the cancerous half of the prostate while leaving the remaining, healthy, portion of the prostate unharmed.

Potential candidates for this approach include men with prostate cancer involving only one-half of the prostate. For this reason, selecting patients for hemiablation requires a specific mapping biopsy (see 3-D mapping biopsy) to be performed in addition to the diagnostic biopsy. Thus we can improve our ability to determine the location and the spread of cancer within the prostate and be able to offer the appropriate treatment for the individual patient.

What are the available devices and technologies used for focal therapy?

There are a number of devices used for focal therapy that represent different methods to destroy cancer tissue within the prostate, avoiding conventional surgery.

The most studied approaches include cryoablation (freezing of the tissue), electrovaporazation (tissue destruction by directing focused electric currents, NanoKnife), HIFU (high intensity focused ultrasound, heating the tissue at the targeted zone), and laser photodynamic therapy (works by light energy amplification).

Cryoablation and HIFU are both done under ultrasound guidance, although by opposite physical principles (freezing and heating, respectively). These are outpatient procedures done under anesthesia and patients are typically discharged the same day.

For cryoablation several small needles are introduced through the perineum into the cancerous part of the prostate to form an ice ball that freezes and destroys cancer tissue. After the completion of the procedure, the needles are removed and a urinary catheter is placed for several days.

The NanoKnife technology passes approximately 90 short electrical pulses between needle electrodes positioned within the ablation zone. These bursts of energy create nano-sized pores in the cell membranes of cancer cells, causing cell death.

There is some evidence that other delicate structures, such as adjacent blood vessels or the erectile nerves, may be spared from destruction with this procedure.

In contrast to cryotherapy or HIFU, the NanoKnife does not use thermal energy (extreme heat or freezing temperatures) to damage tissue. NanoKnife treatments are performed transperineally in an outpatient setting.

Learn more about prostate cancer:

• 3-D Transperineal Prostate Mapping Biopsies
• Prostate Cancer Facts
• Cryosurgery for Prostate Cancer