Percutaneous microwave ablation (MWA) is a promising treatment strategy for patients with cT1-stage renal tumors, but more research into patient risk stratification and selection is needed, as MWA carries a risk of major bleeding and genitourinary-tract complications, according to researchers from the Mayo Clinic in Rochester, Minnesota, who published a retrospective review in the American Journal of Roentgenology (AJR).1

The findings are the latest data to bolster the case for MWA efficacy against kidney tumors.1-7

MWA involves percutaneous positioning of needle-like applicators into tumors to heat and kill tumor cells with microwave heat. It creates coagulative necrosis similar to radiofrequency ablation, which delivers high-frequency electrical currents to create heat. Unlike MWA and radiofrequency thermal ablation, cryoablation uses very cold temperatures to kill tumor tissue. 

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Antenna placement can be guided using computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound (US). 

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“We prefer ultrasound because it involves no radiation; has the ability to continuously watch during the antenna placement and ablation; has high soft-tissue contrast; and has greater flexibility relative to MRI or CT when choosing a site to enter the skin,” said Shane Wells, MD, assistant professor of diagnostic radiology at the University of Wisconsin-Madison in Madison.

When renal tumors are inaccessible through the use of ultrasound antenna placement, CT can be used instead, according to Dr Wells (who is also a consultant for Ethicon, Inc). MRI, an alternative to CT and ultrasound guidance, is used at a minority of institutions.

In the current Mayo study, estimated 3-year local progression-free survival and cancer-specific survival were 96% and 94%, respectively.Overall, 19% of patients experienced complications; 2 patients had minor complications and 3 (11.5%) suffered grade 3 or higher major bleeding and urinary tract complications. One patient died.1

But other, larger studies suggest the procedure has a better safety profile than what was described in the Mayo stusy.3,4