MedPage (KC) 09 Mar 09
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SIR: Cryoablation Freezes Out Kidney Tumors
SAN DIEGO, March 9 -- Cryoablation effectively eradicates kidney tumors less than 5 cm and could be almost as good for larger tumors, researchers said.
Cryoablation yielded a 97% primary efficacy rate overall in eliminating all traces of renal cell carcinoma with 98% disease-specific survival at an average one-year follow-up, Christos Georgiades, M.D., Ph.D., of Johns Hopkins Hospital, and colleagues reported.
The few patients treated for 5- to 10-cm tumors in the single-center case series saw near 100% efficacy with cryoablation as well, they reported here at the Society of Interventional Radiology meeting.
Despite this tantalizing signal, Dr. Georgiades emphasized that the experience with larger tumors is too limited to support conclusions.
His research group also presented safety findings with no treatment-related deaths and 6% morbidity, which they called a "very safe procedure."
These findings, which update preliminary data presented last year at the same conference, should lead to a paradigm shift in kidney cancer treatment Dr. Georgiades said. (See: SIR: Percutaneous Cryoablation Effective Against Kidney Cancer)
"Percutaneous cryoablation should be the first choice treatment" for patients with accessible renal cell carcinoma under 5 cm, he said. "Larger lesions can be staged if the patient is not a surgical candidate."
The efficacy study included all 90 cryoablation procedures done in 84 patients at Johns Hopkins from April 2006 through December 2008.
The cryoablation technique cooled tissue around the probe tip until an "iceball" seen on CT imaging extended at least 4 mm beyond the margins of the tumor.
Patients were under moderate sedation with sometimes no more than a local anesthetic for the essentially painless minimally invasive procedure.
All cases were considered a technical success.
The primary efficacy rate -- defined as no enhancement of a previously enhancing lesion that gradually declined in size after treatment -- was 97%. Two patients had residual disease.
The secondary efficacy rate was 98% after one patient was retreated with complete response.
Overall survival at a median 12 months of follow-up was 97%; the corresponding disease-free survival was 98%.
One patient with small pre-existing lung metastases died from post-obstructive pneumonia during follow-up; a second died from starvation and dehydration after refusing oral intake during a major depressive episode.
For the six tumors 5 to 7 cm in diameter, efficacy was 100%.
Three nonresectable 10-cm tumors were treated with 67% efficacy. One patient had 1 cm of residual viable tumor after treatment but refused to return to complete ablation.
For the subgroup of patients with at least 2.5 years of follow-up, outcomes remain similar to the overall cohort, Dr. Georgiades said.
Dr. Georgiades cautioned that at his institution, all patients with percutaneously accessible tumors -- not just those that are not surgical candidates -- are referred by a urologist for ablation, a process that introduced referral bias to the study.
While radiofrequency treatment on the opposite side of the thermal ablation spectrum has been reported as an option for these patients as well, he said he always chooses cyroablation to avoid the need for anesthesia.
The more important factor in choosing between ablation methods, though, should be operator experience, he said.
Medical oncologists will likely want to see five- and 10-year follow-up, commented Kelvin Hong, M.D., also of Johns Hopkins, who was a co-author on the study and moderated the session at which the findings were presented.
"But certainly it's impressive that as a community we're getting results with percutaneous ablation that are resembling the results achieved with surgical options," Dr. Hong said.
A safety study of the procedure -- presented by Ziga Cizman, of Johns Hopkins and Jefferson University in Philadelphia -- revealed predominantly mild adverse events.
But 1% of patients experienced a life-threatening event, and 5% had events of moderate severity that required treatment. These included:
Two transfusions for patients with delayed bleeding one week after cryoablation when resuming warfarin (Coumadin) One intubation in a patient that hid treatment for pneumonia because he feared cancellation of cryoablation One percutaneous nephrostomy for ureteral stricture or fistula Two chest tubes for pneumothorax in one case and effusion after intentional crossing of the pleura in the other case Drs. Georgiades and Cizman reported no conflicts of interest.
Primary source: Society of Interventional Radiology Source reference: Cizman Z, et al "Percutaneous cryoablation for renal cell carcinoma: efficacy" SIR 2009; Abstract 19.
Additional source: Society of Interventional Radiology Source reference: Cizman Z, et al "Percutaneous cryoablation for renal cell carcinoma: Safety" SIR 2009; Abstract 18.
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