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Long term surveillance may be needed for patients after renal cryoablation, according to study data presented at the 2008 meeting of the Radiological Society of North America (RSNA).

"MRI successfully detects local progression and that this local progression may manifest after a long delay, suggesting that the surveillance is needed for the long term in these patients," reported Erick M. Remer, MD, Director, Associate Prof of Radiology at the Cleveland Clinic, Cleveland, Ohio, who presented the study. (Read the abstract here.) "A comparison of ablation site size reduction over time shows marked shrinkage and involution at the ablation site over time. In fact, many of the ablation sites completely involute and disappear and all that remains is a cortical scar in the kidney where the tumor used to be, resulting in upwards of 70% complete involution by 5 years."

A series of patients had laparoscopic renal cryoablation followed with imaging from September 1997 to September 2007. "The laparoscopic ablation was guided by both laparoscopic ultrasound and direct visualization employing standard cyroablation technique using double freeze thaw cycles," stated Dr. Remer. All patients that comprise the series had five year or longer imaging follow-up. Time to local progression ranged from 6-58 months showing that some patients had local progression fairly early in the first year; but others went out to the 4-5 year time range.

CT-guided core needle biopsy of the ablation sites were performed at 6 months in 80% of patients (67/84). Of those, 66 of the 67 patients had negative biopsy and no abnormal MRI findings. Only 1 of the 67 patients had a positive biopsy and the MRI imaging findings were positive as well. "Therefore," Dr. Remer explains, "MRI imaging had a good concordance with pathology." Of the 56 patients with pathologically proven renal cell carcinoma (RCC), there was local progression in 8.9%:  3 (5.4%) patients had local progression alone and 2 (3.6%) patients had local progression with metastatic disease (with 1 patient having had prior surgery for RCC in the past. Also, there were 3 (5.4%) patients who had distant metastases alone without local progression. "All 3 of these patients had a history of contralateral tumor so there are confounding variables obscuring whether the distant metastasis was from the tumor that was ablated or the tumor that had been resected," Dr. Remer pointed out, adding, "Also, there was no local progression or distant metastases in patients with benign pathology—as would be expected."

In conclusion, the study suggested that renal tumors show marked involution after cryoablation, depicted with MRI. "About 9% of these patients with proven RCC had local progression in this series," Dr. Remer told MedicExchange. "Finally, the true treatment success in this series was confounded the fact that some of these patients had prior metachronous RCC and these tend to be higher stage tumors than the ones that were ablated."

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