For some small kidney cancers, freezing is more effective than heat treatment

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Depiction of ablation of renal cell carcinoma

For patients with early-stage renal cell carcinomas (RCCs) that measure between 3 and 4cm, cryoablation yields a lower risk of cancer-related death compared to thermal ablation, reports a preliminary study in the Journal of Urology.

“In contrast, for patients with RCCs smaller than 3cm, either cold-based or heat-based therapy is just as effective in reducing cancer-specific mortality,” comments lead author Gabriele Sorce (San Raffaele Scientific Institute, Milan, Italy). “The findings may help us to better tailor the choice of ablation technique for patients with small RCCs.”

Lower risk of cancer death with cryoablation versus heating

Renal cell carcinoma is the most common type of kidney cancer. For patients with early-stage RCCs smaller than 4cm, an increasingly popular treatment option is destroying the cancer by freezing it or heating it. For these clinical stage T1a RCCs, ablation can provide high survival rates without the need for more extensive kidney surgery.

However, the outcomes of ablation appear “less favourable” for a subset of patients with clinical stage T1a RCCs: those whose tumours are between 3 and 4cm in size. Current European guidelines recommend cryoablation over thermal ablation for these cancers measuring 3 to 4cm, while US guidelines state that either treatment can be used. Both sets of guidelines state that either freezing or heating can be used for T1a RCCs measuring 3cm or smaller.

To clarify the issue, an international research group analysed patients with stage T1a RCCs treated with freezing or heating between 2004 and 2018. Patients were drawn from the US National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program. The study focused on two matched groups of patients with cancers measuring between 3 and 4cm: 757 treated with cryoablation and 388 treated with thermal ablation.

Median age at treatment was 71 years. Follow-up data on cancer-specific mortality were available for 422 patients treated with freezing and 238 treated with heating.

Eight years after treatment, estimated cancer-specific mortality among patients with RCCs measuring 3 to 4cm  was 8.5% for patients treated with cryoablation versus 12.9% for those undergoing heat-based thermal ablation. With both treatments, about 40% of patients died from causes other than cancer.

Implications for treatment decisions in ‘small, potentially curable’ kidney cancers

After adjustment for non-cancer-related death and other characteristics, patients undergoing thermal ablation for RCCs between 3 and 4cm were twice as likely to die of kidney cancer. In contrast, for patients with cancers smaller than 3cm, estimated cancer-specific mortality was similar between groups: 6.8% after cryoablation and 6.1% after thermal ablation.

The study is one of the first to directly compare clinical outcomes for freezing versus heating in patients with stage T1a RCCs measuring between 3 and 4cm. The results suggest that thermal ablation has “a highly statistically significant and clinically meaningful” disadvantage in terms of the long-term risk of death from kidney cancer, compared to cryoablation.

“Conversely, in patients with tumours 3cm or smaller, either ablation technique is equally valid,” says Sorce. “We believe our findings have important implications for clinical decision-making and informed consent for patients with these small, potentially curable kidney cancers.”


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