Computed Tomography Contrast Enhancement Following Renal Cryoablation—Does it Represent Treatment Failure?

Objective: For minimal invasive treatment of small renal masses, cryoablation has gained popularity. Treatment success is defined as the absence of contrast enhancement on postoperative imaging of the cryoablated lesion, but contrast enhancement does not necessarily equal treatment failure. This present study investigates the proportion of spontaneous resolutions after initial contrast enhancement in relation to cryoablation. Materials and Methods: Data were collected from a prospectively maintained clinical database containing all patients treated with primary laparoscopic and percutaneous cryoablation between August 2005 and December 2013. All images were evaluated with regard to preoperative aspects and dimensions used for an anatomical classification (PADUA) score, cryolesion size, contrast enhancement pattern, and tissue density. Results: A total of 107 patients with a biopsy-verified malignant tumor were included in the study. On postoperative imaging, 33 (31%) patients presented with contrast enhancement. Spontaneous resolution was observed in 15 (45%) patients after a mean follow-up time of 14 months. Patients with cryolesions that resolved spontaneously were found to have a less anatomical complex tumor compared to patients with treatment failure (PADUA 7.8 vs 9.5, p<0.01). A total of seven patients with a PADUA score 10 and contrast-enhancing cryolesions were found to have treatment failure. No association was found among body mass index, histology, treatment modality, enhancement pattern, number of applied cryoprobes, and resolution. Conclusion: Postoperative contrast enhancement is commonly observed after cryoablation and a large portion of these lesions often resolves spontaneously, thus not representing treatment failure. In patients with a high preoperative PADUA score and postoperative contrast enhancement of the cryolesion, treatment failure or recurrent disease should be suspected.