Ablation of renal tumors shows 6% recurrence rate

August 1, 2011

The recurrence rate following thermal ablation of renal cortical tumors is 6%. About half of recurrences can be managed successfully with salvage ablative procedures, but 20% require extirpative surgery.

"You could argue that it's very important to counsel patients on what the recurrence rate is after an ablative procedure and how these are managed because the national trends for ablation are increasing for patients with index renal masses," first author Jay Raman, MD, told Urology Times.

Although partial nephrectomy is becoming the standard for managing localized renal tumors, both cryoablation and radiofrequency ablation represent minimally invasive alternatives to partial nephrectomy. In the 2009 AUA guidelines for the management of small renal masses, ablation and active surveillance are presented as options for patients with clinical T1a tumors who have major comorbidities and thus are at increased surgical risk, said Dr. Raman, associate professor of urology at Penn State Milton S. Hershey Medical Center, Hershey, PA.

Of the 390 patients who had them managed by cryoablation, 47% were done laparoscopically and 53% percutaneously.

Recurrence was defined in one of three ways: incomplete primary ablation at the time of the first imaging study post-treatment, ablation zone recurrence, or metastatic and/or extra-renal disease.

6.1% recurrence rate observed

Seventy-seven patients (6.1%) developed a recurrence at a mean of 13.7 months. There was no significant difference in recurrence rate between cryoablation and radiofrequency ablation (4.9% vs. 6.6%, respectively; p=.22). Mean tumor size of the failures was 3.3 cm.

"As expected, two-thirds were endophytic, 50% were interpolar, and 63% were posterior in location," said Dr. Raman, who presented the study results at the AUA annual meeting in Washington.

Of the 77 initial ablation recurrences, 47 (61%) were an incomplete primary ablation, 29 (38%) were ablation zone recurrences, (mean: 20.3 months post-ablation), and one (1%) with an 8.4 cm tumor had metastatic disease. Twenty-one of the patients with radiographic failures underwent biopsy, all of which were positive for renal cell carcinoma.

Fifty patients had salvage ablation, which was successful in 38 patients (12 patients had recurrence after salvage). Partial or radical nephrectomy was performed in 13. Fourteen patients were managed with surveillance.

Of the 12 recurrences after salvage, six had repeat salvage ablation (three of whom had successful repeat salvage ablation; three had recurrence while on surveillance), three were managed with active surveillance, and three underwent radical nephrectomy.

Sixteen patients underwent surgical salvage: five with partial nephrectomy and 11 with radical nephrectomy. The pathology in these 16 patients included renal cell carcinoma in 10 (clear cell, eight; papillary, two) and necrosis/fibrosis in four. In the 10 with renal cell carcinoma, seven were stage pT1a and three were stage pT3a.

At a mean of 28 months, 53 patients had no evidence of disease, 16 were alive with disease, four were dead of disease, and four died of other causes. The actuarial cancer-specific and overall survival was 94.8% and 89.6%, respectively, at the most recent follow-up.

"If you look at how we defined recurrence rates, incomplete ablations accounted for the vast majority of the 6%. It is a little bit concerning that we had a recurrence rate of about 5% to 6% at 1 to 1.5 years after the ablative procedure," said Dr. Raman.

These data provide valuable information to urologists counseling patients who are interested in renal ablative procedures, he said.