Early results from a small retrospective study showed that percutaneous microwave ablation (MWA) had a technical success rate higher than 95% for both T1a and T1b renal cell carcinomas.1 The technical success rate for T1a tumors was 96% and 100% for T1b tumors.

“Despite significant comorbidities and obesity in our patient cohort, technically successful MWA were achieved for all but 1 case of T1a RCC and for all cases of T1b RCC,” the researchers wrote.

Researchers reviewed records for 29 patients treated with microwave ablation at a single institution from March 2013 to June 2014. Researchers identified 30 tumors, of which 23 were T1a and 7 were T1b. Median age was 66 years and 69% of the cohort was male. Median body mass index was 30 and median Charlson comorbidity index was 3.5.

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Researchers assessed technical success using contrast-enhanced computed tomography immediately after ablation. It was determined that the procedure achieved technical success in all but 1 instance, which was an oval-shaped T1a tumor. That patient, however, was successfully retreated with salvage ablation, conferring a secondary effectiveness of 100%.

The authors noted some limitations, however: the patient population was small, the treatment procedure was performed at a single institution, follow-up was relatively short, and the study was retrospective. Nonetheless, Thomas J. Polascik, MD, professor of surgery and director of the Society of Urologic Oncology Program at Duke University in Durham, North Carolina, said he was encouraged by the findings, and wanted to see large prospective studies of microwave ablation with longer follow-up.

“You have to keep in mind that with any kind of new technology, one always starts with small steps,” he said. “This looks very promising, but the bottom line is that the procedure is being performed for kidney cancer and making assessments at a mean of 11 month’s follow-up, which is not sufficient. I’d start noticing the results at about 5 years.”

Regardless, the results were promising: out of 28 patients, 23 were assessed for local tumor progression for at least 6 months, and researchers observed no progression at a median imaging follow-up of 12 months, for a progression-free survival of 100%. Cancer-specific survival was 97% and overall survival was 93%.

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There were 2 Clavien-Dindo grade 2 complications, both of which appeared after hospital discharge. One patient developed pneumonia, which required hospitalization and intravenous antibiotics. Another patient developed cystitis that was managed with oral antibiotics. All patients recovered fully. There were no Clavien-Dindo grade 3, 4, or 5 complications.

“I’m encouraged. The preliminary outcomes look good; the results seem consistent. Some of the early studies with MWA suggested that there may be inconsistencies.”


  1. Wells SA, Wheeler KM, Mithqal A, Patel MS, Brace CL, Schenkman NS. Percutaneous microwave ablation of T1a and T1b renal cell carcinoma: short-term efficacy and complications with emphasis on tumor complexity and single session treatment. Abdom Radiol (NY). 2016;41(6):1203-1211.