Words of wisdom. Re: Partial nephrectomy versus radical nephrectomy in patients with small renal tumors--is there a difference in mortality and cardiovascular outcomes?

Experts’ summary: Huang and coworkers examined whether radical nephrectomy (RN) is associated with an increase in cardiovascular events and mortality compared with partial nephrectomy (PN). The study sample was obtained from Surveillance, Epidemiology, and End Results (SEER), a consortium of population- based cancer registries that includes approximately 26% of the US population. The primary end points of the analysis were cardiovascular events, cardiovascular deaths, and allcause mortality after renal surgery. The study cohort included nearly 3000 patients with definitive surgery for a renal tumor of _4 cm diagnosed between 1995 and 2002. Of these patients, 18.6% underwent PN and 81.4% underwent RN. A total of 609 patients had at least one cardiovascular event after surgery, including 84 (15.1%) in the PN group and 525 (21.6%) in the RN group. Of the 892 deaths, 173 were attributable to cardiovascular causes. In the PN and RN groups, 27 (4.9%) and 146 patients (6.0%), respectively, died of cardiovascular causes. When adjusting for preoperative demographic and comorbid variables, RN was associated with 1.4 times more cardiovascular events after surgery ( p < 0.05). However, RN was not significantly associated with time to first cardiovascular event (hazard ratio [HR]: 1.21; p = 0.10) or with cardiovascular death (HR: 0.95; p = 0.84). Experts’ comments: The interest in PN for small localized renal tumors has increased in the last decade because it ensures maximal parenchymal preservation along with oncological efficacy. Several recent studies showed that for tumors <7 cm, PN provides excellent cancer-specific survival and recurrencefree survival rates, equivalent to those achieved with RN [1– 3]. In contrast, RN invariably leads to a substantial decrease in the number of glomeruli, and the functional kidney loss is particularly relevant if RN is performed for pT1 tumors. The susceptibility to renal failure is determined, in large part, by glomerular number: People with fewer nephrons, whether through reduced endowment or excessive loss such as after RN, have a higher rate of glomerulosclerosis and fewer nephrons to lose before their renal excretory function becomes terminally compromised [4–7]. A recent publication confirmed that RN represents a detrimental factor for the development of chronic kidney disease (CKD), with a 3-yr probability of freedom from new onset of stage 3 CKD being 80% after PN and 35% after RN ( p < 0.001); corresponding values for stage 4 CKD were 95% and 64% ( p < 0.001), respectively [8]. The limited amount of functional renal tissue removed by PN causes no or only mild adaptive hyperfunction that is mainly related to the duration of ischemia,while a substantial ablation of renalmass such as after RN can cause adaptive hyperfunction and hypertrophy leading to a statistically significant increase in renal failure rate [4,8–10]. In the present paper, the authors take a step forward, trying to evaluate if RN adversely influences nononcological outcomes through the development of CKD and its association with cardiovascular disease. They found that as a consequence of substantial kidney function loss, RN is associated with 1.4 times more cardiovascular events after surgery than PN. RN was not significantly associated with time to first cardiovascular event (HR: 1.21; p = 0.10) or with cardiovascular death (HR: 0.95; p = 0.84), but preexisting renal disease was shown to significantly predict type of surgery. This finding could have potentially mitigated the power of the results reported and could explain this lack of correlation. The maximal preservation of renal tissue in patients undergoing surgery for renal tumors is of the utmost importance for several reasons: The glomerulosclerosis rate is inversely correlated with the total number of glomeruli; aging is associated with a significant decline in glomerular number; many conditions such as hypertension, stone disease, and diabetes can further affect the kidneys; and tumors can recur elsewhere in the kidney, such as contralateral renal cell carcinoma (RCC) [2,3]. As experience with PN and the efficacy of the hemostatic agents increase, the indications for the conservative management of RCC are expanding. In our department, PN is performed in 90% and 50% of single sporadic tumors of <4 cm and 4–7 cm, respectively; thus, the number of PNs performed has exceeded the number of RNs since 2002 [2]. In conclusion, RN is not the best treatment for most clinically T1 kidney tumors because it puts patients at risk of CKD and cardiovascular disease. PN minimizes these risks, which is a further reason to expand its indications. Conflicts of interest: The authors have nothing to disclose. References [1] Becker F, Siemer S, Humke U, Hack M, Ziegler M, Sto¨ ckle M. Elective nephron sparing surgery should become standard treatment for small unilateral renal cell carcinoma: long-term survival data of 216 patients. Eur Urol 2006;49:308–13. [2] Minervini A, Lapini A, Serni S, Carini M. Nephron-sparing surgery for renal cell cancer–Current indications in a tertiary referral centre. Eur Urol Rev. In press. [3] Ljungberg B, Hanbury DC, Kuczyk MA, et al. Renal cell carcinoma guideline. Eur Urol 2007;51:1502–10. [4] Fulladosa X, Moreso F, Narva´ez JA, Grinyo´ JM, Sero´n D. Estimation of total glomerular number in stable renal transplants. J Am Soc Nephrol 2003;14:2662–8. [5] Nyengaard JR, Bendtsen TF. Glomerular number and size in relation to age, kidney weight, and body surface in normal man. Anat Rec 1992;232:194–201. [6] Hoy WE, Douglas-Denton RN, Hughson MD, Cass A, Johnson K, Bertram JF. A stereological study of glomerular number and volume: preliminary findings in a multiracial study of kidneys at autopsy. Kidney Int 2003;63:S31–7. [7] Kappel B, Olsen S. Cortical interstitial tissue and sclerosed glomeruli in the normal human kidney, related to age and sex. A quantitative study. Virchows Arch A Pathol Anat Histol 1980;387:271–7. [8] Huang WC, Levey AS, Serio AM, et al. Chronic kidney disease after nephrectomy in patients with renal cortical tumors: a retrospective review. Lancet Oncol 2006;7:735–40. [9] Lhotta K, Eberle H, Konig P, Dittrich P. Renal function after tumor enucleation in a solitary kidney. Am J Kidney Dis 1991;17:266–70. [10] Fine LG. How little kidney tissue is enough? N Engl J Med 1991;325:1097–9. Andrea Minervini, Sergio Serni, Marco Carini* Department of Urology, University of Florence, Careggi Hospital, Florence, Italy