De Novo Renal Tumors Arising in Kidney Transplants: Midterm Outcome after Percutaneous Thermal Ablation

Purpose: To retrospectively evaluate the midterm outcome of patients treated for primary renal cell carcinomas arising in kidney transplants with minimally invasive techniques. Materials and Methods: The institutional review board of each participating institution approved this retrospective study and waived informed consent. This study was HIPAA compliant. A request for cases through the European Society of Urogenital Radiology network was made to institutions for patients who fit the requirements outlined by the authors, and a prospective follow-up of recipients was performed. Twenty-four tumors were identified that developed in the renal allograft of 20 patients from 11 institutions who were treated with radiofrequency ablation (n = 19) or cryoablation (n = 5) between 2003 and 2010. Maximal diameter of masses was 6-40 mm (median, 19.5 mm). Twenty masses were solid, and four were type 4 cystic masses. Preablation biopsy was performed for solid tumors only. All images and biologic and biopsy reports were retrospectively reviewed. Significant differences were determined by using a paired t test before and after ablation. Results: Mean follow-up was 27.9 months (range, 7-71 months). Histopathologic examination revealed papillary carcinoma in 17 patients and clear cell carcinoma in three. Tumors were successfully treated with ultrasonographic guidance in six patients, with computed tomographic guidance in 10 patients, and with both in four patients. One case of infection of the tumor site and one case of transitory genitofemoral nerve injury were the only reported complications. No significant change of renal function was noted. Subsequent imaging follow-up did not reveal any case of recurrence in the ablative site. Conclusion: Percutaneous thermal ablation of renal tumors occurring in renal grafts is effective, with low morbidity. (C) RSNA, 2011