Cryoablation versus Partial Nephrectomy for Clinical T1b Renal Tumors: A Matched Group Comparative Analysis.

BACKGROUND

The traditional treatment for a cT1b renal tumor has been radical nephrectomy. However, recent guidelines have shifted towards partial nephrectomy (PN) in selected patients with cT1b renal tumors. Furthermore, practitioners have extended the role of cryoablation (CA) to treat cT1b tumors in selected patients.

OBJECTIVE

To evaluate the efficacy of CA compared to PN for cT1b renal tumors.

DESIGN, SETTING, AND PARTICIPANTS: We performed a retrospective review of patients who underwent either renal CA (laparoscopic or percutaneous) or PN (robot-assisted) for a cT1b renal mass (>4cm and ≤7cm) between November 1999 and August 2014. To reduce the inherent biases of a retrospective study, CA and PN groups were matched on the basis of key variables: tumor size, Charlson comorbidity index (CCI), age, body mass index (BMI), American Society of Anesthesiologists (ASA) score, preoperative serum creatinine, preoperative estimated glomerular filtration rate (eGFR), gender, and solitary kidney. The matching algorithm was 1:1 genetic matching with no replacement.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Survival analysis was performed only for patients diagnosed with renal cell carcinoma according to histopathologic evaluation of a tumor biopsy or resected tumor specimen. Recurrence-free, overall, and cancer-specific survival were analyzed using Kaplan-Meier survival curves. Survival outcomes were compared between groups using the log-rank test.

RESULTS AND LIMITATIONS

A total of 31 patients were treated using CA and 161 using PN during the study period. After matching, there was no significant difference between the PN and CA groups for tumor size (4.6 vs 4.3cm; p=0.076), CCI (6 vs 6; p=0.3), RENAL score (9 vs 8; p=0.1), age (68 vs 68 yr; p=0.9), BMI (30 vs 31kg/m; p=0.2), ASA score (3 vs 3; p=0.3), preoperative creatinine (1.2 vs 1.4mg/dl; p=0.2), preoperative eGFR (63 vs 53ml/min/1.73 m; p=0.2), and proportion of patients with a solitary kidney (19% vs 32%; p=0.4). The total postoperative complication rate was higher for PN than for CA (42% vs 23%; p=0.10). There was no significant difference in percentage eGFR preservation between PN and CA (89% vs 93%; p=0.5). The rate of local recurrence was significantly higher for CA than for PN (p=0.019). There was no significant difference in cancer-specific mortality (p=0.5) or overall mortality (p=0.15) between the CA and PN groups.

CONCLUSIONS

Patients treated with CA for cT1b renal tumors had a significantly higher rate of local cancer recurrence at 1 yr compared to those treated with PN. Until further studies are performed to clearly define the role of CA in cT1b renal tumors, CA should be reserved for patients with imperative indications for nephron-sparing surgery who cannot be subjected to the risks of more invasive PN.

PATIENT SUMMARY

We evaluated the efficacy of renal cryoablation compared to partial nephrectomy for clinical T1b renal tumors. The cryoablation and partial nephrectomy groups were matched to provide a better comparison. We concluded that renal cryoablation had a higher rate of local cancer recurrence.