On-clamp versus Off-clamp Partial Nephrectomy: Propensity Score Matched Comparison of Long Term Functional Outcomes
The elective indication for off-clamp (Off-C) partial nephrectomy (PN) in patients with good baseline renal function remains controversial. The aim of this study is to compare the risks of developing a severe (stage ≥3b) chronic kidney disease (CKD) in patients with cT1-2/N0/M0 renal tumors and baseline estimated glomerular filtration rate (eGFR) >60 ml/min after either Off-C or on-clamp (On-C) PN.
Materials and Methods
A prospective “renal cancer” database of two high volume centers was queried for “cT1-2/N0/M0” tumors, "PN" and “baseline eGFR>60 mL/min”. Overall 1073 patients met the inclusion criteria (483 Off-C and 588 On-C). A 1:2 propensity score-matched (PSM) analysis was employed to minimize the selection bias of non-random treatment assignment of patients.
Kaplan–Meier method was used to compare the PSM cohorts specific risks of developing a CKD stage ≥ 3b during follow-up in the PSM cohorts, and the log-rank test was applied to assess statistical significance between groups. Univariable and multivariable Cox regression analyses were performed to identify independent predictors of developing a CKD stage ≥3b.
On-C patients were significantly younger (p=.001), less frequently smokers (.01), with a lower incidence of diabetes (.001) and hypertension (.001), lower ASA scores (<.001), higher baseline eGFR values (.003), smaller tumor sizes (<.001), and higher incidence of positive surgical margins (.021).
After applying the PSM analysis, the two cohorts of 221 On-C and 485 Off-C PN cases did not differ for all clinical and pathologic covariates (Table 1; all p ≥ .06).
The probability of developing a CKD stage ≥ 3b was significantly higher (log rank p=.006, Figure 1) in the On-C cohort (2, 5 and 8yr risk 0.9, 5.1 and 12.8% vs 0.6, 1.2 and 1.2% in the Off-C cohort, respectively). On-C technique was associated with a 5.2 fold increased risk of developing CKD stages ≥3b compared with the Off-C approach (HR 5.2 [95% CIs 1.4–18.9]; p=.012).
At multivariable regression analysis, eGFR at discharge and Off-C PN were independent predictors of outcomes. For each increasing mL/min of eGFR at the discharge the risk of developing a CKD stage ≥3b was reduced by 5% (HR 0.95 [95% CIs 0.93–0.97]), while On-C approach was associated with a 5.8 fold increased risk of developing a CKD stage ≥3b (HR 5.8 [95% CIs 1.6-20.8]).
This study highlights the beneficial role of an Off-C approach in patients with cT1-2/N0/MO renal tumors and good baseline renal function candidate to elective PN.
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