To describe 2 patients with tumor progression after treatment with radiofrequency ablation (RFA). RFA is a minimally invasive, Food and Drug Administration-approved technique used to treat solid organ tumors. However, few studies of RFA treatment failure have been reported.

As a part of an institutional review board-approved protocol, nine renal tumors were ablated with RFA during a 2-year period. Patients enrolled on the protocol were assigned to one of two arms—ablate and resect and ablate and follow-up—depending on the patient’s health, tumor characteristics, and tumor location and size. The average tumor size was 4.5 cm in the largest dimension, and the tumors were accessed percutaneously using computed tomography or ultrasound guidance, with direct laparoscopic visualization or through an open incision for concomitant nephrectomy. Postoperative follow-up examinations occurred at 3-month intervals for 2 years using serial computed tomography or magnetic resonance imaging.

Two patients (22%) in the ablate and follow-up arm of the study experienced significant tumor progression less than 1 year after RFA. One tumor increased in size by 20% and the other quadrupled in size and developed a renocolic fistula. This is the first reported case of a renocolic fistula after RFA of a renal tumor. Both patients subsequently underwent radical nephrectomy with the final pathologic results showing renal cell carcinoma.

Rapid tumor progression and renocolic fistula formation are possible complications of RFA. This treatment requires close and aggressive follow-up to ensure complete eradication of the renal lesion.