Published in UAB Insight, Summer 2008
Patient Selection, Use, and Follow-up for Cryoablation of Small Tumors
Physicians will diagnose more than 54,000 new cases of kidney cancers in 2008, according to American Cancer Society estimates. Traditionally the preferred surgical appro-ach for removal of a renal tumor is radical nephrectomy, which can reduce long-term renal function. In indicated cases, however, partial nephrectomy has replaced radical nephrectomy as the gold standard for renal tumor removal. This technique preserves remaining normal renal parenchyma in the affected kidney.
Widespread use of imaging technologies has led to a rise in incidental detection of renal tumors <3 cm, particularly among persons aged 65 to 84 years (EAU-EBU Update Series. 2007;5:206-218). Interest in the development and use of alternative nephron-sparing procedures has paralleled increasing early detection of small tumors.
UAB is now offering cryoablation, a newer nephron-sparing technique, to patients with renal cancers. "Recent improvements in cryoablation have increased our understanding of its best application," says UAB urologic cancer surgeon J. Erik Busby, MD. Compared with partial nephrectomy, cryoablation of small, solid renal masses offers patients several benefits, including decreased blood loss, less pain, and shorter recovery periods.
"Patients with a solid renal mass less than 3.5 cm whose health status rules out partial nephrectomy or who would not consider surgical removal of the tumor are optimal candidates for the procedure," he says. "Such candidates include individuals with compromised renal function, older individuals, or those with mitigating comorbidities. Patients also may be considered for cryoablation if they are not comfortable with active surveillance," Busby says. "Cryoablation of these tumors can be performed laparoscopically, which requires an overnight stay. When the tumor is in an ideal location, it can be approached percutaneously by interventional radiology - this can be done in an outpatient setting or may require an overnight stay. Either way, recovery is faster than with partial nephrectomy."
Outcome, Follow-up, and Efficacy
Cryoablation initiates tumor necrosis with liquid argon or nitrogen administered during ultrasound-guided laparoscopy. Tumors become in situ ice balls and form necrotic tissue that is absorbed over time.
Follow-up for cryoablation requires long-term vigilant monitoring using computed tomography (CT) scans, magnetic resonance imaging (MRI), or ultrasound. Traditional surgical intervention does not require repeated, frequent imaging analysis, which may be an issue for some patients, Busby says.
Follow-up imaging initially takes place every 3 to 6 months with a diminishing frequency over time. Renal function guides the choice of imaging modalities used for long-term monitoring. In patients with impaired renal function, for example, repeated use of contrast media to enhance CT and MRI images is contraindicated. In addition, concerns about patients' exposure to radiation through frequent CT scans may prompt use of MRI or ultrasound to follow disintegration of the necrotic lesion. Cryoablation of small renal tumors is an important addition to the therapeutic options for patients with kidney cancers, allowing physicians to individualize treatment for their patients, Busby says.
"Short-term efficacy rates are in excess of 90% for cryoablation, although the length of follow-up for this modality is still somewhat short - only 3 years - versus more than a decade for partial nephrectomy," he says. "Proper application of this technology in the correct population is key to successful outcomes."
FOR MORE INFORMATION:
Dr. Erik Busby
1.800.UAB.MIST
mist@uabmc.edu