Real-Time Magnetic Resonance Imaging–Guided Focal Laser Therapy in Patients with Low-Risk Prostate Cancer

Excerpts below:

Abstract

Two patients with low-risk prostate cancer (PCa) were treated with outpatient in-bore magnetic resonance imaging (MRI)–guided focal laser ablation.

The tumor was identified on MRI. A laser fiber was delivered via a catheter inserted through a perineal template and guided to the target with MRI. The tissue temperature was monitored during laser ablation by MRI thermometry. Accumulated thermal damage was calculated in real time. Immediate post-treatment contrast-enhanced MRI confirmed devascularization of the target. No adverse events were noted. MRI-guided focal laser therapy of low-risk PCa is feasible and may offer a good balance between cancer control and side effects.

Once the catheter reached its target, the metal trocar was replaced by an optical fiber with a 1-cm-long cylindrically diffusing tip attached to a 980-nm diode laser (Visualase Inc, Houston, TX, USA).

During laser ablation, temperature was measured simultaneously on five 3-mm-thick image slices that covered the target volume (Fig. 5a). The thermometry scan was repeated every 6 s.

Fig. 5 (a) Tissue temperature map measured by magnetic resonance thermometry (echo planar imaging with multiphase; field of view: 25 × 25 cm; matrix 256 × 256; number of excitations: 1; repetition time: 545 ms; echo time: 20 ms; flip angle: 20°; slice thickness: 3 mm) during laser ablation; (b) a map of the tissue volume exceeding the threshold damage for coagulation was superimposed on the anatomical image, with the pink line measuring the maximum diameter of the ablated tissue.

The MRI thermometry software (Visualase, Inc, Houston, TX, USA) allowed us to monitor temperature at specific points in the tissue. The temperature at those points was used as a feedback to control the laser. During the laser heating, the temperatures at the border of the rectal wall and urethra were monitored and maintained at safe levels by shutting down the laser automatically when the temperature at these critical points exceeded 45 °C. Thermal damage was calculated using an Arrhenius formula. Temperature and damage maps were superimposed onto anatomic images (Fig. 5b). Once the desired volume of tissue destruction was achieved, laser power was stopped.

The patients were discharged home within 3 h. MR scans performed 2 wk post-treatment showed no evidence of complications with preservation of rectum and neurovascular bundles. No adverse effects were noted at ≤1 mo after treatment. Six-month follow-up biopsies are pending.

Outpatient MRI-guided FLT as used in the present study allows for visualization of the tumor; real-time guidance of the thermal device to the target; monitoring and control of the zone of ablation and surrounding tissue during treatment; and the ability to immediately confirm the success of the treatment and, if necessary, immediately repeat therapy. The required skills are common to other minimally invasive procedures, resulting in a short learning curve for the surgeon. Refinement of this outpatient procedure may result in an inexpensive, minimally invasive alternative to current active therapies. Further trials will be necessary to define the safety and oncologic efficacy of this therapy, but our early results are promising.

Acknowledgment

The authors would like to thank Drs. Ashok Gowda and Roger McNichols of Visualase Inc., Houston, Texas, USA, for generously supplying the laser and magnetic resonance thermometry system and for their technical support of this study.

Read the full article case study.

Visualase To Be Awarded $2.1 Million For Prostate Cancer Research.

Visualase Inc. was selected for a $2.1 million grant from the Cancer Prevention and Research Institute of Texas. The precision and control of the Visualase technology has made possible the ablation of tissue in areas such as brain and prostate.

Houston, TX  February 10, 2010 — Visualase Inc. announced today that it has been selected for a grant $2.1 million from the Cancer Prevention and Research Institute of Texas (CPRIT). On January 20, CPRIT Chief Science Officer Dr. Al Gilman, announced awards to 16 institutions based in Texas which are on the forefront of cancer research and treatment. Visualase is one of only two private companies to receive such a grant and stands with established cancer institutions such as The University of Texas M.D. Anderson Cancer Center, Baylor College of Medicine, and UT Health Science Centers, among others.

Visualase Technology. Brain image during treatment.

“We’re thrilled to be recognized by the Cancer Prevention and Research Institute of Texas and we’re looking forward to accelerating our efforts in providing patients in Texas and across North America with better treatment options for prostate cancer. Doctors Ashok Gowda and Roger McNichols deserve all of the credit for not only developing our technology, but also collaborating with health professionals to make an immediate impact on improving patient outcomes,” CEO Bill Hoffman said.

The focus of the grant will be continued clinical exploration of focal treatment of cancerous tumors in the prostate, a treatment which could significantly reduce the rate of side-effects associated with conventional “whole gland” treatments, including prostatectomy and whole gland irradiation. The clinical study to be funded by the grant will be lead by a team from M.D. Anderson Cancer Center.

The unprecedented level of precision and control afforded by the Visualase technology has made possible ablation of tissue in highly sensitive areas such as brain and prostate. Doctors are currently using the system for ablation of brain, prostate, liver, bone, and other solid tumors. For more information about the Visualase Technology and Visualase Inc., visit http://www.visualaseinc.com.

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Prostate Cancer Research Projects

University of Chicago

Dr. Scott Eggener

“A Study to Evaluate Magnetic Resonance Thermal Image-guided Laser-Induced Thermal Therapy for Pinpoint destruction of Prostate Cancer.”

This human clinical trial, approved by the FDA, will test a treatment that can eliminate prostate cancer cells without damaging the surrounding tissues. The research team will evaluate the feasibility of a FDA-approved thermal therapy and feedback system (Visualase® Thermal Therapy System) for the treatment of biopsy confirmed and MR-imageable prostate lesions. This system has been used in humans for the treatment of brain, spine,thyroid, and liver cancers; however it has not yet been evaluated for the primary treatment of prostate cancer.

This system allows delivery of laser energy while the patient is simultaneously being imaged by an MRI unit. The system’s real-time MR thermal imaging (MRTI) provides information on the thermal dose delivered to the target, resulting in a more precise and controlled delivery which has not been possible with other cancer removal therapies. The researchers hypothesize the system can be a practical and feasible treatment for low-risk localized prostate cancer and allow patients to avoid the complications associated with radical whole-gland therapy. This clinical trial will take up to 2 years. PFC Funding Partners-The Longest Day of Golf Chicago and the University of Chicago Foundation.