On-clamp versus Off-clamp Partial Nephrectomy: Propensity Score Matched Comparison of Long Term Functional Outcomes
To compare renal functional outcomes after either off-clamp (Off-C) or on-clamp (On-C) PN in patients with cT1- 2/N0 M0 renal tumors and baseline estimated eGFR >60 ml/min.
Materials and Methods
A prospective 'renal cancer" database of two high volume centers was queried for cT1-2/N0/M0 tumors and baseline eGFR>60 mL/min. Overall 1073 patients met the inclusion criteria, 588 On-C PN and 485 Off-C PN. A 1:3 propensity score-matched (PSM) analysis was employed to minimize the potential selection bias.
Joinpoint regression analysis was used to plot the 2 to 8 yrs probabilities of experiencing eGFR decreases of 0%,< 25% and between 25 and 50% in both PSM cohorts and, therefore,to compare the trends for each of these 3 subgroups.
Kaplan-Meier method was used to compare the risk of developing a CKD stage>=3b during follow-up in the PSM cohorts. Univariable and multivariable analyses were performed to identify independent predictors of developing a CKD stage>=3b.
In the whole cohort On-C patients were significantly younger (p=0.001), less frequently smokers (p=0.01), with a lower incidence of diabetes (p=0.001) and hypertension (p=0.001), lower ASA scores (p<0.001), higher baseline eGFR values (p=0.003), smaller tumor sizes (p<0.001), longer warm ischemia time (17 minutes vs 0, p<0.001) and higher incidence of positive surgical margins (p=0.021). After applying the PSM analysis, the two cohorts of 157 On-C and 471 Off-C PN cases did not differ for all clinical and pathologic covariates (all p>0.08), except for mean warm ischemia time (p<0.001).
At Joinpoint regression analysis Off-C group displayed significantly higher probabilities of maintaining unmodified eGFR after surgery (p=0.02), and significantly lower probabilities of experiencing eGFR decrease >25% in the first 8-yr follow-up (p=0.02).
The probability of developing a CKD stage>=3b was significantly higher (log rank p=0.006) in the On-C cohort (2, 5 and 8yr risk 0.9%, 5.1% and 12.8% versus 0.6%, 1.2% and 1.2% in the Off-C cohort, respectively.
At multivariable Cox regression analysis, eGFR at discharge (HR 0.94; 95% CIs 0.91-0.98, p=0.002) and Off-clamp approach (HR 7.33; 95% CIs 1.8-29.4, p=0.005) were independent predictors of improved renal functional outcomes.
Off-C PN is associated with a significantly higher probability of maintaining 100% eGFR after surgery compared with On-C PN in patients with cT1-2/N0/MO renal tumors and good baseline renal function candidate to elective PN. Patients treated with On-C PN had a 7.3 fold increased risk of developing a severe CKD during follow-up.
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