The impact of cryoablation on renal function: a comparison of endophytic vs exophytic renal tumors

To compare long-term renal function after computed tomography (CT)-guided cryoablation for endophytic versus exophytic renal tumors.

Materials and Methods:

A retrospective analysis of 464 CT-guided cryoablations between 2014 and 2024 was performed. Endophytic tumors, defined by location within 5 mm of the renal sinus fat and no protrusion beyond the kidney contour, were compared to a matched cohort of exophytic tumors, defined as those with >50% protrusion beyond the renal contour. Renal function was represented by glomerular filtration rate (GFR). GFR < 60 was defined as renal dysfunction. Pre-procedure GFR was compared to post-procedure GFR obtained at 3 months, 6 months, 1 year, and 3 years post-procedure. Parametric statistical tests, such as unpaired t-tests and z-test of proportions, were performed to compare variables between the two groups. Statistical significance was determined by α = 0.05.

Results:

Of the 464 procedures performed, 62 endophytic tumors were compared to a matched cohort of 63 exophytic tumors. Pre-procedural renal dysfunction (GFR < 60) did not differ between the endophytic group (23/62) and exophytic group (19/63, p = 0.41). Other baseline patient and treatment characteristics (e.g., age, sex, BMI, history of diabetes or hypertension, tumor size, and number of probes used to treat) were not statistically different. In the endophytic group, mean GFR initially decreased by 11% from preoperative GFR at 3 months post-procedure, then demonstrated a recovery to 6% below preoperative GFR by 6 months and stabilized to 7% and 8% below preoperative GFR at 1 year and 3 years, respectively. In the exophytic group, mean GFR initially decreased by 2% from preoperative GFR at 3 months, then continued to decrease to 5% below preoperative GFR by 6 months and stabilized to 9% below preoperative GFR by 3 years. There was no statistical difference in the proportion of patients with renal dysfunction after 3 years in the endophytic group (32/62) versus the exophytic group (32/63, p = 0.93). One patient in both groups developed renal failure (GFR < 20) by 3 years post-procedure.

Conclusion:

While cryoablation of endophytic tumors, as compared to exophytic tumors, results in a greater initial decrease of mean GFR within 3 months post-procedure, mean GFR in both groups stabilizes to a similar level by 3 years post-procedure.