Tumour ablation techniques have proved their worth as successful options for treating cancer. Existing methods such as cryoablation, radiofrequency ablation and microwave ablation use intense heat or cold to destroy cancer cells. But there's another promising variant emerging: irreversible electroporation (IRE). Based on electricity rather than heat, advocates of IRE claim that it offers highly targeted ablation with minimal post-operative pain.
IRE works by using electric pulses to permanently open microscopic pores in cell membranes. The cells in the targeted tissue then die within six hours of treatment, with little or no damage to surrounding healthy tissue such as nerves, blood vessels and other critical structures. The electrical pulses are delivered via a needle (or needles), making this a minimally invasive option.
One of IRE's novel advantages is that that the generated electrical field is not affected by the proximity of blood vessels. Heat-based ablation techniques, on the other hand, may be compromised in areas of excessive vascularization, as the flowing blood can transfer heat or cold away from the treatment site. Meanwhile, IRE's sparing of blood vessels and lymphatic systems surrounding the targeted site means that they remain to assist the body in removing the dead cells.
The technique was first used in humans in April 2008, with five prostate-cancer patients treated in Florida as part of a pilot clinical trial. This first clinical application of IRE to ablate soft tissue was deemed "completely successful", based on analysis of biopsies performed two weeks after treatment.
Earlier this month, clinicians at Rhode Island Hospital (Providence, RI) used IRE to treat a 70-year-old female, in the first IRE ablation of a kidney tumour in the US. The patient is reported to be doing well. The procedure was performed by Damian Dupuy, director of ablation services at Rhode Island Hospital and a national pioneer in ablation treatment.
"I'm excited about the continued advances in ablation technology that broaden the applications for patients with cancer," Dupuy said "These new technologies are revolutionizing the way we are able to treat cancer, allowing us to minimize collateral damage to surrounding tissue while maximizing tumour kill."
Both of the above IRE ablations were performed using the NanoKnife image-guided IRE system from AngioDynamics (Queensbury, NY). Approved by the US Food and Drug Administration for general soft-tissue ablation, the NanoKnife has also been used at The Alfred in Melbourne, Australia, with six tumours (in the liver, kidney, lungs and lymph nodes) treated to date.
The NanoKnife uses up to six probes (1 mm in diameter, 15 cm long, with an active electrode length of 0-40 mm) that can be placed at fixed distances apart in the tissue to create various two-pole configurations. The probes can be sited to cover the entire mass or repositioned during treatment, using ultrasound or CT visualization to guide placement.
Because IRE is minimally invasive, Dupuy says that the new technology can offer additional treatment options to patients who have no other alternatives or who have not responded to other forms of cancer treatment. In certain locations, he told medicalphysicsweb, the NanoKnife may one day even become a first-line treatment.
• AngioDynamics is sponsoring a symposium later this week examining "First Human Clinical Experience with IRE Technology". Held in New York City on January 22, the event will see doctors who have performed procedures using the NanoKnife system share their experiences and patient outcomes.