Elective nephron sparing surgery decreases other cause mortality relative to radical nephrectomy only in specific subgroups of patients with renal cell carcinoma

Abstract

Purpose:

There is no consensus regarding a protective effect on mortality due to a cause other than cancer in patients treated with elective nephron sparing surgery relative to their radical nephrectomy counterparts. We test whether the protective effect of nephron sparing surgery relative to radical nephrectomy is universal or present in specific subgroups of patients.

Materials and Methods: A collaborative database of 5 institutions was queried to evaluate 1,783 patients without chronic kidney disease diagnosed with a clinical T1 renal mass that was treated with nephron sparing surgery or radical nephrectomy. Multivariable Cox regression analysis was done to assess the impact of surgery type (nephron sparing surgery vs radical nephrectomy) on other cause mortality after adjustment for patient and cancer characteristics. Interaction terms were used to test the hypothesis that the impact of surgery type varies according to specific subcohorts of patients. Results: Ten-year other cause mortality-free survival rates were 90% and 88% after nephron sparing surgery and radical nephrectomy, respectively. In the overall population radical nephrectomy was not associated with an increased risk of other cause mortality on multivariable analysis compared to nephron sparing surgery (HR 0.91, 95% CI 0.6–1.38, p = 0.6). However, radical nephrectomy increased the risk of other cause mortality according to the increasing baseline Charlson comorbidity index (interaction test p = 0.0008). For example, in a patient with a Charlson comorbidity index of 4 the probability of 10-year other cause mortality-free survival was 86% after nephron sparing surgery and 60% after radical nephrectomy. Conclusions: Elective nephron sparing surgery does not improve other cause survival relative to radical nephrectomy consistently in all patients with kidney cancer. Patients who are more ill with relevant comorbidities are those who benefit the most from nephron sparing surgery in terms of other cause mortality. Nephron sparing surgery represents the standard of care for patients diagnosed with a cT1a renal mass.1–4 Similarly, NSS should be preferred over RN when technically feasible in patients diagnosed with a cT1b renal mass.1,2,4 The rationale of these recommendations in favor of NSS is to decrease the risk of chronic kidney disease5–7 as well as the risk of cardiovascular events8,9 while maintaining similar cancer control. However, the controlled comparison of NSS vs RN presented in the EORTC 30904 trial showed no difference with respect to cancer specific mortality but lower ACM after RN,10 implying a paradox advantage with respect to OCM after RN. Methodological limitations of this trial have been used to justify such a counterintuitive result and prompted further observational investigations that revealed the opposite finding, namely lower OCM after NSS relative to RN.9,11–15 Recently, the inherent risk of bias in such observational studies9,11–15 has been highlighted.16,17 It was postulated that if present, a beneficial effect of NSS on OCM has yet to be proved.18 In this light the aim of the study was to examine the impact of surgery type, namely NSS vs RN, on the risk of OCM in a large multi-institutional study that allowed for adjustment for a detailed panel of intrinsic confounders such as BMI, CCI, and the presence and type of hypertension or diabetes. Our hypothesis stated that NSS might be associated with a lower risk of OCM and such a benefit might be more evident in specific subgroups of patients.