Minimally invasive focal therapies for prostate cancer

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.