Kidney Tumor Ablation Ideal for Selected Patients
LONDON—Ablation techniques are an ideal treatment option for some patients with kidney cancer, said Alice Gillams, MRCP, FRCR, Consultant Radiologist, The London Clinic, Harley Street.
Dr. Gillams told attendees at the Renal and Bladder Cancer 4th National Conference about about her experience with ablation techniques for renal cancer. Having performed cryotherapy and radiofrequency ablation (RFA) on hundreds of patients since 1996, Dr. Gillams said she thinks these are promising and well-established treatment options for select patients.
Ablation therapies are a particularly good option for patients who are not fit for surgery. The ideal tumor is small (less than 5 cm), peripheral, and exophytic. Ablation also is safer than surgery. The complication rate for laparoscopic partial nephrectomy is 30%, compared with less than 10% for cryotherapy and 2%-7% with RFA.
Cyrotherapy uses hollow needles that are placed inside the tumor to freeze tissue. Different imaging techniques can be used to monitor the cryotherapy procedure, such as ultrasound, magnetic resonance imaging, or computed tomography.
“Cryotherapy is injury by ice formation, and this causes cellular disruption. The standard is a double freeze-thaw cycle: You freeze again and you thaw again. You really need that double freeze-thaw cycle to get good cell injury,” Dr. Gillams explained. “Originally, the cryoprobes were very big, and [the procedure] could only be done only at open surgery, but now we have 17-gauge percutaneous probes.”
RFA is “very very different,” Dr. Gillams said. “It is an alternating current that alternates within the 375-480 khz range, and that causes ionic agitation so the probe itself does not get hot. The ions in the tissue around the probe agitate and get hot with frictional heating.”
Dr Gillams said she predominantly uses a cool tip device, which gives clinicians the option of using a single needle or three needles mounted on one handle.
The procedure can be laparoscopic and ultrasound guided, but a percutaneous approach is another option. It is much more minimally invasive and a good technique for anterior tumors, Dr. Gillams said. She said she typically performs a contrast-enhanced imaging study immediately after each RFA procedure to evaluate what has been achieved. “Dead tissue does not enhance with RFA so absent enhancement denotes cell death.”
A criticism of ablation is that it is not possible to get a biopsy or sample of tissue to stage the cancer, but Dr. Gillams said that she routinely does a percutaneous biopsy on her ablation patients. “Percutaneous biopsy has now come of age,” she said.
Tumor size and location are important, she noted. “We are very good at peripheral tumors, but not very good at central tumors; they tend to come into the center of the kidney, sitting next to blood vessels, and blood vessels are a problem for ablation.”
The blood flowing in the vessels acts “like a sort of fan, gently cooling the tumor and potentially protecting it.” Although it is possible to treat tumors sitting on blood vessels, there is a greater likelihood of incomplete ablation, she said.
“I don't think there is much question that the percutaneous approach is safer,” Dr. Gillams said. “It really is a very simple, uncomplicated procedure, it's quite short, there is a very limited hospital stay, there is a very quick convalesce, and the laparoscopic approach carries some trocar-specific complications.”
Referring to an earlier talk at the meeting on robotic-assisted partial nephrectomy Dr. Gillams said she was impressed with the technique, “but I could have done three ablations in that time.”
“I think both RFA and cryotherapy are real contenders for the effective treatment of small renal masses,” Dr. Gillams told listeners. Doctors should base their selection of treatment modality on the tumor, the patient, and their own confidence in performing the procedure.