PD51-12 Comparison of mid-term oncological outcomes of active surveillance and percutaneous cryoablation of small renal masses

INTRODUCTION AND OBJECTIVES Partial nephrectomy (PN) is considered the standard approach for small renal masses (SRMs). Active surveillance (AS) and ablative therapies represent emerging strategies for older and comorbid patients due to the indolent behaviour of most SRMs and to the high competing risk mortality. Aim of this study was to compare the mid-term oncological outcomes of AS and percutaneous cryoablation (PCA) of small renal masses (SRMs). METHODS Data regarding PCA and AS in patients with a single T1a renal tumors were collected prospectively at two large academic centers. 60 patients underwent PCA and 77 were enrolled in a AS protocol. The minimum follow-up period was 6 months. The most frequent indications for AS were severe comorbidities (48,1%), <15 mm renal masses (23,4%) and advanced age (15,6%). All patients in AS were followed with a standardized protocol including serial imaging (US, CT or MRI) every 6 months during the first 3 years and yearly thereafter. Tumor progression was defined as the reach of a 4 cm threshold in maximum diameter or a tumor volume doubling time <12 months. All PCA procedures were performed with a percutaneous approach. A double freeze-thaw cycle was performed using a mean of 2 sealed argon 17G cryoprobes per patient. Tumor progression after PCA was defined as a new nodular enhancement in the ablation zone or the enlargement of the ablated tumor 3 months after the treatment. RESULTS 14 masses showed dimensional progression during AS and 9 were surgically removed after a median follow-up of 30 months. 3 patients in the PCA group experienced progression and underwent a repeat ablation with a median follow-up of 24 months. Progression free survival (PFS) at 2 years was 94,8% and 95,0% for AS and PCA group, respectively. None of the patients progressed to metastatic disease. Overall survival at 2 years was 93,5% and 95,0% in the AS and PCA group, respectively. In the PCA group the complication rate was 5% (Clavien grade 1-2). CONCLUSIONS There are no good quality studies comparing the oncological outcomes of AS and PCA. Comparing AS to an active treatment is not an easy task due to the different definitions of the oncological endpoints such as PFS. With these limitations this study shows that both AS and PCA represent viable and safe treatment options for elderly and comorbid patients with SRMs.