Focal Laser Ablation of Prostate Cancer: An Office Procedure

I’m Dr.Leonard Marks, speaking from the urology department at UCLA. A new approach to prostate cancer treatment, Focal Laser Ablation, offers the potential for cancer cure without the side effects of surgery or radiation. And, as we’ll show here, it can be done in an outpatient clinic under local anesthesia.

We offered to men with intermediate risk prostate cancer. The idea came from a group of dedicated clinical scientists coming together from urology, radiology, pathology and biomedical engineering, all coming together 10 years ago seeking a common goal to make prostate interventions more accurate and cancer treatment more effective than it had been in the past. The new method begins with multiparametric MRI.

Here, the three image sequences reveal in the prostate a highly suspicious grade five lesion. MR/ultrasound fusion biopsy confirms an intermediate risk Gleason seven cancer. Biopsy core locations are stored for future reference as needed.

In the next step, the MRI is sent to an image fusion device and the lesion is fused or incorporated into a live ultrasound image. The lesion can then be targeted for biopsy. We reasoned that if a biopsy needle can be placed into the lesion like this, why not use the same approach to place a laser fiber into the lesion and ablate it.

In Focal Laser Ablation, tissue is heated using infrared light energy to cause coagulation necrosis. The Orion device enables the physician to perform focal laser ablation in a clinic setting using only ultrasound for guidance. The device includes a laser catheter, thermal sensor probe for tissue monitoring, and workstation.

The laser catheter is a composite needle comprising of a diffusing laser fiber, a flow channel to circulate coolant and ultrasound imaging markers. Laser heating is controlled during treatment in real time using an interlocking sensor probe, also inserted into the patient. This probe monitors thermal and optical tissue response for safety.

If temperatures exceed safety limits, the system automatically shuts off laser heating. During treatment, a three-dimensional heat map and expected tissue damage is overlaid onto a patient-specific prostate model in order to evaluate treatment progress in relation to critical structures. A patient-specific treatment plan is made by combining MRI and pathology data.

The MRI-visible lesion, in combination with cancer positive biopsy cores, tell us where the tumor is. Of equal importance are the benign biopsy cores, which tells us where the tumor isn’t. By mapping them out in 3D, we can create a treatment margin around the tumor that includes all positive cores and excludes negative ones.

This approach treats the tumor while sparing most healthy prostate tissue and preserving quality of life. Laser positions are chosen to encompass the treatment margin. Each ablation has a maximum diameter of 18 millimeters, which is overlaid on MRI.

The ablations are overlapped to ensure there are no gaps in treatment and positioned to treat beyond the prostate to compensate for capsular cooling. A good plan should minimize damage to the urethra. Once the physician is satisfied, this patient-specific treatment plan is loaded onto the Orion for visualization during the procedure.

In preparation for the procedure, place a laser-warning sign outside of the room and minimize all non-essential traffic. While setting up the room, the workstation is placed where it can be comfortably accessed. An IV bag of saline and a drainage bag are attached to the workstation to facilitate later cooling of the laser fiber during ablation.

The IV tubing is passed through the pump on the front of the workstation and coiled for later use. 60 minutes prior to the procedure, patients receive antibiotic prophylaxis, oral acetaminophen and intramuscular The multi-channel guide is placed over the ultrasound probe in a similar fashion to setting up a biopsy guide. The center channel of the guide is for placement of the laser catheter and for anesthetizing the prostate.

The lateral channels are for placing the thermal probe. The right and left orientation will change depending on the treatment plan. The patient is positioned in the left lateral decubitus position in similar fashion to a transrectal biopsy.

Vital signs are taken at the beginning of the procedure and may be taken periodically during the ablation. Insert the transrectal probe as for biopsy, and anesthetize the prostate in the usual fashion. Following anesthesia, image fusion is performed in the same manner as a fusion biopsy.

At UCLA, we have experience with the Artemis device. However, the Orion system is not platform-dependent and can be used with other fusion systems to guide treatment. Once the fusion system has generated a 3D model of the prostate, this is fused with the diagnostic MRI and treatment plan.

Next, the ultrasound is guided to the first ablation zone using information overlaid from the MRI and treatment plan. On the left is a 3D model of the prostate, with urethra in purple, ROI in red, and three planned ablations marked in green, blue and pink. The yellow circle represents the orientation of the ultrasound probe relative to the prostate.

On the right, this information is overlaid on the live 2D ultrasound image to guide the practitioner to the desired ablation site. Once at the desired ablation site, the 14 gauge laser catheter is inserted into the center channel of the guide. Note that the guide is curved to provide gentle friction and prevent treatment elements from slipping backward during ablation.

Rotation of the laser catheter while penetrating the prostate capsule may facilitate insertion. The laser catheter is advanced until four echogenic markers pass centrally through the hourglass shape target. The prostate may shift relative to initial fusion with placement of the laser catheter.

The depth of the laser catheter relative to the planned ablation can be evaluated on live ultrasound by referencing the prostate capsule. The ablation zone begins five millimeters distal to these echogenic markers and spans a treatment area 27 millimeters in length and 18 millimeters in diameter. The thermal probe is placed in non-ablated tissue to the left or right of the laser catheter, depending on the lesion location and treatment plan.

The thermal probe contains eight thermocouples to monitor treatment throughout the ablation zone. The thermal probe magnetically locks to the laser catheter when at the proper depth and orientation. Because the thermal probe is eight millimeters offset from the laser catheter, it will not be visible on the ultrasound during placement.

Connect the IV tubing from the saline bag to the proximal port on the laser catheter and the return tubing to the distal port on the laser catheter. The operator is now ready to begin the first ablation. On the Orion workstation, select the ablation site that corresponds to the laser catheter position.

Confirm the ablation plan selection to begin circulating saline around the laser catheter. Perform the safety checklist displayed on the left side of the screen. Laser safety goggles are donned, including the patient.

The appropriate positioning of the echogenic bands relative to the prostate capsule is confirmed. Finally, the Orion system will automatically load treatment parameters and check that each thermal couple within the temperature probe is uniformly reading body temperature. Once the safety checklist is complete, the operator may then press the Start Laser button.

Temperature recordings will appear on the left side of the screen that evaluate multiple thermocouple positions within the thermal probe. The thermocouple closest to the rectum is displayed as a white line. This temperature should not exceed 42 degrees, and will trigger an automatic stop if this temperature is reached.

The thermocouple closest to the laser tip is marked in blue and will gradually increase in temperature after laser activation. The thermal probe will cause an automatic shutoff if the laser tip temperature exceeds 75 degrees. The intervening thermocouples are displayed as gray lines.

A pink line shown here corresponds to an experimental optical sensor which may monitor tissue ablation in the future. Approximately five minutes is required for each ablation. A damage map based on the Arrhenius equation uses time and temperature data collected from the thermal probe to visually estimate the progression of ablated tissue.

This damage map will display as yellow pixels which progressively fill the ablation outline. With each treatment location, the damage map is expanded to fill the treatment plan. Individual ablations are halted by the practitioner when the temperature plateaus without further increase over time, temperatures at the ablation outline reach 60 degrees, or a portion of the ablation approaches critical structures such as the urethra.

After stopping the laser, saline is allowed to flow until temperatures are below 42 degrees, thus preventing rectal wall heating upon withdrawal of hot treatment elements. For subsequent ablations, the laser and thermal probe are moved into position by rotating or angling the ultrasound probe as needed. The operator reconfirms co-registration.

If needed, a motion compensation is performed to realign the MRI and ultrasound images. Repeat the process previously described to perform subsequent ablations. Once all ablation sites have been treated, press the Finish Treatment button.

As you have just seen here, Focal Laser Ablation with the Orion device, while still investigational, is a promising new treatment for prostate cancer. In the trial so far, oncologic efficacy appears favorably with other treatments. It can be performed under local anesthesia in an outpatient clinic and side effects are few.

Thank you.