New Treatment for Once-Inoperable Cancers
By Mary Jo Blackwood, RN, MPH
Steven Strasberg, MD, performs irreversible electroporation (IRE).
For patients with liver tumors near delicate structures such as major blood vessels or bile ducts, the diagnosis of inoperable cancer may have changed. For nearly a year, Steven Strasberg, MD, hepatobiliary pancreatic cancer surgeon, has been performing a procedure called irreversible electroporation (IRE).
The procedure involves a NanoKnife and placement of electrodes around the tumor. A high-voltage direct current creates holes in targeted cell membrane and irreversibly damages cancer cells. The surrounding veins, nerves and ducts remain largely unaffected. With the cancer cells destroyed, healthy tissue can grow and repopulate the area.
Over the last decade, Strasberg has performed hundreds of radiofrequency (RF) ablation surgeries for patients with liver cancer, but he recognized a need for a surgery like IRE for patients with liver tumors located near major vessels or bile ducts.
"We think there are many people out there with complex liver tumors who have been told they are inoperable, " Strasberg said. "We want to let them and their oncologists know that IRE is available and is FDA-approved."
Strasberg says that IRE can be used in any part of the liver.
How IRE Works
Strasberg uses an MRI to locate the tumor within the liver. Using ultrasound guidance, he surgically exposes the liver and places needle electrodes in the correct locations.
Strasberg explains: "The needles must be at a specific depth, parallel to each other and a specific distance apart. We use anywhere from three to five needles, depending on the size and configuration of the tumor, to kill mostly cancer cells and spare nearby healthy tissue."
Once the electrodes are in place, Strasberg enters information into the NanoKnife machine that allows it to confirm correct placement. The machine then automatically delivers electrical current in coordination with the patient's EKG pattern and heartbeat.
"The current is delivered during the 10 millisecond period of cardiac rhythm rest," he said. "By treating during this refractory period, the current cannot interfere with normal heart rhythms."
Strasberg says delivery of the current takes about 10 to 15 minutes, but the entire surgical procedure can take two hours. Six weeks after IRE, the patient has an MRI to confirm tumor destruction.
Contraindications for IRE
Patients who aren't eligible for IRE fall into several categories:
- Those whose tumors are too large or too numerous.
- Those who have implanted pacemakers or defibrillators, devices not currently included in FDA approvals for this procedure.
- Those who have very fast or irregular heartbeats. Safety factors built into the NanoKnife system prevent it from identifying the refractory period if the heartbeat is erratic or too fast. In such cases, the machine won't deliver a current.