Overview
Focal One® High-Intensity Focused Ultrasound.
What is focal therapy for localized prostate cancer?
Focal therapy is a treatment for prostate cancer of low to intermediate aggressiveness that is completely contained (localized) within the prostate.
For many years there have been two main approaches to managing 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 isn’t spreading. No other action is taken because the cancer is stable or growing so slowly it won’t cause problems right away. If tests show the cancer is spreading, treatments can begin. Of those men assigned to active surveillance, about one-third will eventually need to have 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 is typically associated with side effects in the urinary, sexual, and bowel function. Two common side effects include loss of control over urinary functions (incontinence) and erectile dysfunction
Focal therapy offers a middle-ground treatment. The idea behind focal therapy is to preserve these functions while still treating the cancer effectively. Focal therapy concentrates on treating “the index lesion,” which is usually defined as a tumor visible on MRI of low or favorable intermediate grade 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 safely while minimizing 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 tissue. In focal ablation, the area of the prostate that contains the index lesion is targeted, rather than treating the entire prostate gland. Focal ablation techniques include:
- Cryotherapy: The 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. Some 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.
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 those with favorable intermediate risk disease (as defined by the NCCN guidelines). The best candidates have a prostate gland of about 40cc in size or a tumor in the lower half of a larger gland, a single visible tumor on MRI, and the absence of cancer elsewhere in the gland (as proven by biopsies).
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.
Dec. 21, 2018
Mayo Clinic offers a unique complement of MRI-directed, image-guided, minimally invasive focal therapies for prostate cancer. The procedure can be another option for selected patients with localized intermediate risk prostate cancer. The idea of focal therapy is relatively new to prostate cancer but has become an accepted approach for treatments for other cancers.
“The goal of focal therapy is to treat only the area with the most aggressive tumor, while leaving the rest of the prostate and its surrounding structures alone,” says Derek J. Lomas, M.D., Pharm.D., a urologist at Mayo Clinic’s campus in Rochester, Minnesota. “This approach is widely accepted in other types of cancer. For example, we commonly treat kidney cancers by removing or ablating only the tumor while leaving the rest of the kidney intact.”
The prostate tumor that is targeted is referred to as the index lesion. In prostates with more than one tumor, this is generally the largest tumor with the highest grade. In these cases, it is believed that the index lesion drives the behavior of the prostate cancer and that treating it alone with focal therapy may lead to good overall cancer control with fewer side effects.
The typical treatment approaches to prostate cancer involve either surgical removal of the entire prostate (radical prostatectomy) or administration of radiation therapy to the whole prostate. These approaches can be associated with side effects such as erectile dysfunction or urinary incontinence. By targeting treatments to the tumor and avoiding structures that surround the prostate, such as the nerves that control erections or the urinary sphincters, providers hope to limit the side effect profile of prostate cancer treatment in properly selected patients.
Focal therapy relies on the use of energy sources to generate extreme temperatures that lead to tumor destruction. Available options include cryoablation, focal laser ablation and high-frequency ultrasound ablation.
MRI-guided focal cryoablation and focal laser ablation are offered clinically. Currently, high-frequency ultrasound ablation is offered only in the setting of an ongoing clinical trial Mayo Clinic. As long-term safety and efficacy data for this approach to prostate cancer therapy is lacking, all patients undergoing these treatments agree to participate in registries so that Mayo researchers can closely follow the patients’ diseases.
Treatment and follow-up
All treatments are performed by a multidisciplinary team consisting of urologists and interventional radiologists. The procedures are performed with the assistance of real-time prostate MRI in Mayo Clinic’s state-of-the-art MRI interventional suite, which was completed in 2018. Patients are placed under anesthesia for the procedure. For cryoablation and focal laser ablation, the ablation probes are placed through small needles inserted into the perineum. For high-frequency ultrasound ablation, the ablation energy is delivered through a transrectal ultrasound probe without the need for any needles.
Depending on the size and location of the tumor, the procedure takes about 2.5 hours. Patients generally spend one night in the hospital for observation and have a urinary catheter in place for one to three days. There are few activity restrictions following removal of the catheter. Typically, patients who undergo surgical removal of the prostate will have up to six weeks of the lifting restrictions and require a urinary catheter for one week.
Focal therapy is suitable for properly selected candidates. While there are no strict criteria for patients selected for focal therapy, optimal candidates have biopsy-proven intermediate risk prostate cancer in only one area of the prostate. Some men with small areas of low-risk prostate cancer in addition to their index lesion may also be candidates. The prostate cancer lesion should also be visible on prostate MRI.
Ongoing follow-up is very important following treatment. Patients can expect follow-up PSA testing every three months initially following treatment. Follow-up prostate MRIs and clinic visits are scheduled every six months to start, and intervals may be increased as more time passes. Repeat prostate biopsy is also important if changes are seen on follow-up MRI or the PSA rises.
If recurrent prostate cancer is found on follow-up, patients may have the option for repeat ablation or they can elect to have whole-prostate gland treatment in the form of radical prostatectomy or radiation therapy.
Focal therapy is a prostate cancer treatment for small tumors that are in only one area of the prostate. This treatment is also known as partial gland ablation. Focal therapy is less invasive, meaning it does less harm to healthy issue. It is a safe and effective treatment for prostate cancer.
Focal therapy uses real-time imaging to guide treatment methods that kill small tumors inside the prostate. It offers benefits over other treatments:
- It can kill areas of cancer in the prostate without harming normal prostate tissue and function.
- There can be fewer and less severe side effects than there are with more aggressive treatments, such as surgery and radiation.
- It can often be done as an outpatient procedure.
MSK’s Approach to Focal Therapy
Focal therapy is not for everyone who has prostate cancer. MSK follows strict standards for recommending who should have it. You must first have a thorough evaluation. MSK experts will confirm your tumor is small and localized (in only one part of the body). We also will make sure we can skip or delay more extensive treatment.
Our goal is to treat the area of the prostate gland that has higher-grade cancer. For the parts of the prostate that have low-grade tumors, we use active surveillance.
After focal therapy, we will monitor you closely using magnetic resonance imaging (MRI) and prostate needle biopsy. These tests tell us if the cancer is gone and let us check if it later returns.
MSK is a leader in studying new technology to use in focal therapy for certain prostate cancers. Some of these new methods are available only through our research studies, known as clinical trials.
MSK has led research studies that show successful short-term results in killing tumors. It’s important to learn if focal therapy keeps cancer from coming back. We are now studying the long-term benefits for people who had this treatment.
Focal Cryoablation
Focal cryoablation uses a needle-thin probe to freeze a prostate tumor.
The probe delivers a solution around the tumor, freezing it at a very low temperature and killing it. In the past, we used this method to treat the whole prostate gland. Now, we use cryotherapy to kill just the tumor while keeping safe most of the healthy prostate. This treatment is best for tumors that are located either away from the rectum or at the top of the prostate. These locations make it possible to keep nearby healthy tissue safe.
High-Intensity Focused Ultrasound
High-intensity focused ultrasound (HIFU) is a prostate cancer treatment that uses the energy of sound waves.
The ultrasound’s sound waves are aimed at the tumor with the help of MRI scans. (It is also called magnetic resonance guided focused ultrasound surgery, or MRgFUS.) This treatment superheats and kills small prostate tumors. We monitor this therapy as it takes place, using the MRI to measure the temperature of the prostate.
MSK has strong experience in treating people with this therapy. We have led research studies, known as clinical trials, that study MRgFUS. The trials have shown that this approach is effective at treating prostate tissue.
NanoKnife® (Irreversible electroporation)
The NanoKnife is a tool used in focal therapy that passes an electrical current through the tumor.
The electricity makes very tiny openings (pores) in the tumor’s cells. This kills the cells. We use ultrasound to focus the current around the tumor, keeping nearby healthy tissue safe. MSK has used this technology, which is also called irreversible electroporation, to treat liver and pancreas tumors. We are leading a clinical trial to study whether the NanoKnife is safe and effective at killing prostate cancer cells.
Follow-Up Care
MSK will carefully monitor your progress after focal therapy. You will have exams and prostate-specific antigen (PSA) testing. You also will have MRI testing and prostate needle biopsy. These tests tell us if your treatment was successful or if the cancer has come back. In some cases, we won’t treat low-risk prostate cancer. Instead, we will monitor you through active surveillance.
Please talk with your healthcare provider to see if you can join MSK’s focal therapy clinical trials. They can refer you to MSK experts who will know if these new treatments are right for you.
