University of Wisconsin School of Medicine and Public Health Madison, Wisconsin, United States
Background: Current AUA guidelines recommend radiofrequency ablation or cryoablation be considered for renal mass < 3cm. Microwave ablation (MWA) has fewer technical limitations and enables larger ablation zones. The purpose of this study was to compare oncologic outcomes for cT1 RCC treated with MWA and surgery.
Methods: A prospectively maintained database of patients with clinically localized RCC treated with either radical nephrectomy (RN), partial nephrectomy (PN), or MWA from 2000 to 2020 was utilized. Local recurrence-free (LRFS), metastasis-free (MFS), and cancer-specific survival (CSS) were estimated using the Kaplan-Meier method. Variables associated with survival were determined using Cox proportional hazard models.
Results: 1209 patients were treated for cT1 RCC (353 MWA, 398 PN, 458 RN). Patients who underwent MWA were older (p < 0.001) and had higher Charlson Comorbidity score (p < 0.001). Median follow-up was 42 months (IQR 21-75).
Compared to surgery, MWA was associated with similar MFS and CSS when adjusting for age, histology, size, and grade (Table). MWA was, however, associated with an increased risk of local recurrence on multivariate analysis (HR 3.79, 95% CI 1.39-10.3). Of the 21 patients with local recurrence following MWA, 12 underwent repeat ablation, 4 had surgery, 4 underwent surveillance, and 1 had SBRT. Of the 12 who underwent repeat ablation, 10 patients were disease-free at median follow-up of 60.5 months.
Among MWA treated lesions, RCC lesions between 3.1-4cm and 4.1-5cm had no difference in LRFS compared to lesions < 3cm. Lesions >5cm had higher risk of local recurrence compared to lesions < 3 cm (HR 3.82, 95% CI 1.02, 14.3).
Conclusions: MWA effectively treats cT1 RCC with similar rates of metastatic progression and cancer specific survival compared to surgery. Local recurrence is more common with MWA, but can be salvaged by a second treatment. MWA effectively treats tumors up to 5cm without compromising recurrence outcomes.
