Comparison of long-term Results after nephron-sparing Surgery and Radical Nephrectomy in Treating 4- to 7-cm Renal Cell Carcinoma

survival in the RN and NSS groups was 69.6% and 80.6%, respectively (log-rank test P=0.198). Pathological stage and patients’ age were the major factors affecting both overall and cancer-specific survival. The type of surgery (NSS or RN) had no effect on survival. Conclusions. Our study showed that nephron-sparing surgery is a safe technique compared with radical nephrectomy that ensures good oncological control in the treatment of renal cell carcinoma measuring 4 to 7 cm and may be proposed as the treatment of choice for renal tumors not only up to 4 cm, but also 4 to 7 cm in size.


Introduction
Renal cell carcinoma (RCC), also known as adenocarcinoma of renal cortical cells, hypernephroma, clear cell carcinoma, or Grawitz tumor, is the most common renal tumor comprising 85% of all malignant renal tumors and 2%-3% of all malignant neoplasms in adults (1,2). The increased frequency of the diagnosis of this disease is associated with the increased use of ultrasound examination back in 1980. RCC is the most lethal neoplastic disease of the urinary system: the mortality of patients with renal cell carcinoma is 56% compared with the mortality of only 20% among patients with prostate or urinary bladder cancer (1). The incidence of this cancer in the general population increases by 2.5% each year (2).
The progress in the diagnostics and treatment of RCC during the last decades has improved survival in individual patient groups. Since 1969, when Robson et al. published the data of their retrospective study on 88 cases of RCC, radical nephrectomy (RN) has become the golden standard in the surgical treatment of this disease. Eventually, the increasing numbers of detected small-size, initial-stage, and better-differentiated renal carcinomas expanded the indications for the application of partial nephrectomy (renal resection or nephron-sparing surgery [NSS]). This was caused by several reasons, one of which being that tumors in 20%-30% of patients following RN were found to be benign. In addition, an increasing body of evidence has indicated no difference in survival, cancer-specific survival, cancerfree survival, or relapse between patients undergoing NSS and those undergoing RN. Other reason was an increased risk of renal failure following nephrectomy, which may impair total survival due to comorbidities such as heart failure (3). Mild or moderate renal failure was documented in 65% and 36% of patients, respectively, following RN and 20% and 5% of patients, respectively, after NSS (4).
Initially, NSS for patients with RCC was applied only in the presence of absolute (imperative) indications: tumor located in one functional kidney (anatomically or functionally single kidney) or a multifocal or bilateral renal tumor. Later on, the indications for NSS were expanded, and the procedure was applied in the presence of relative indications as well. Recently, the significance of NSS has been increasing in treating renal tumors when the function of the contralateral kidney remains normal, i.e. in the presence of elective indications. NSS indicated for RCC measuring 4 to 7 cm (stage T1b) had equivalent oncological results to those in patients who underwent RN (5)(6)(7)(8)(9). However, the significance of NSS in the presence of RCC measuring 4 to 7 cm has insufficiently been studied compared with RCC less than 4 cm in diameter.
The aim of our study was to compare long-term oncological outcomes following NSS and RN for RCC 4 to 7 cm in diameter.

Material and Methods
After the approval of the Regional Ethical Committee, 351 patients who underwent NSS or RN between January 1998 and December 2009 were included into the study.
Patients were considered eligible for entry into the study if they had solitary RCC measuring 4 to 7 cm and underwent RN or NSS for relative or elective indications. All of the patients underwent surgery with an open method. Patients with multiple or bilateral tumors, distant metastases, benign tumors in pathology specimens and those who underwent laparoscopic surgery were excluded from further analysis. Patients who underwent NSS for absolute indications (functionally or anatomically single kidney tumor) were excluded from the study as well.
The studied groups were compared with respect to the patients' age, sex, status according to the American Society of Anesthesiologists (ASA) criteria, tumor size, the grade of differentiation (G), pathological stage (pT), histological type, time in surgery, the rate of complications, and the duration of in-hospital stay.
Information on the status of these patients (alive or deceased, and the cause and the date of death) was gathered from the National Cancer Control and Prevention Center. The last registered date of passive observation was March 31, 2012. Depending on the cause of death, OS and CSS were evaluated.
Statistical data analysis was performed by using the SPSS 17.0 software. Categorical data were tested by using the chi-square test or the Fisher exact test as appropriate, and continuous data were tested using the Student t test. The Mann-whitney test was used when data were not normally distributed. Overall survival (OS) and cancer-specific survival (CSS) were established using the Kaplan-Meier method, and curves were tested with the log-rank test. The effect of potential risk factors on survival was evaluated using a multivariate Cox regression model. The level of statistical significance was set P<0.05.

Results
During the study, 351 patients underwent surgery for RCC measuring 4 to 7 cm: 317 patients (90.3%) underwent RN, and 34 patients (9.7%), NSS. The characteristics of the studied population and patients divided into the RN and NSS groups are presented in Table 1.
The mean follow-up was 6.44 years: 6.46 years in the RN group, and 6.23 years, in the NSS group (P=0.744). In total, 133 patients (37.9%) died during the study: 123 patients (38.8%) died in the RN group, and 10 patients (29.4%), in the NSS group (P=0.283).
The analysis of the causes of death in 133 patients showed that 76 (57.2%) died from renal carcinoma, and in 51 patients (38.3%), the cause of death was other disease. In 6 cases (4.5%), the cause of death was unknown; therefore, these subjects were excluded from the specific mortality analysis.
In the RN group, the 5-year CSS was 80.9%; 7-year CSS, 76.4%; and 12-year CSS, 69.6%. In the NSS group, the 5-year CSS was 97.1%, and the 7-and 12-year CSS, 80.6%. Even though CSS was better in the NSS group, the difference was not significant (log-rank test P=0.198) (Fig. 3).
The factors that significantly affected OS were the subjects' age, pT, G, and preoperative ASA class. Each year of age increased the risk of death by 1.033-fold. The increase of the ASA class or G by one point increased the risk of death by 1.7-and 1.6-fold, respectively. The increase of the pT (pT1 vs. pT2 vs. ≥pT3) by one unit increased the risk of death by 1.4-fold. OS was not affected by the surgical technique or tumor size (Table 2).
CSS was significantly affected by the subjects' age, pT, and ASA functional class. The most significant factor that increased the risk of death by 2.28-fold was tumor G. CSS was not affected by the surgical technique or tumor size (  As a result of two studies conducted at the end of the last decade of the 20th century, 4 cm was "accidentally" selected as the greatest tumor size allowing for NSS. One of these studies, carried out by Hafez et al. (11), reported that 5-year survival was significantly better in the groups with renal tumors measuring <4 cm compared with the group of patients where the tumor size was >4 cm (96% vs. 86%). However, it is noteworthy that in the group of larger tumors, NSS was performed in the presence of absolute indications in 91% of the cases, 30% of the tumors were >7 cm in size, and no control group of patients undergoing RN was used. These data were used as the basis for selecting the margin of 4 cm when defining indications for elective NSS, and T1 tumors in the TNM classification were divided into the T1a (<4 cm) and T1b (4 to 7 cm) categories. It has been proven that NSS performed in patients with renal cell carcinoma and a solitary tumor of ≤4 cm (T1a) provides relapse-free long-term survival similar to RN (5-8). During the recent years, the significance of NSS in treating tumors exceed-ing 4 cm has been attracting increasing attention.
In one of the most recent and largest studies conducted by Crepel et al. (9), the 5-year cancer-specific survival in the presence of T1b RCC in the NSS group reached 91.4% compared with 95.3% in the RN group. Slightly different results were reported in a study by Patard et al. (8), where cancer-specific survival in the presence of RCC measuring >4 cm was better, but not significantly, in the NSS group (93.8%) than the RN group (91.0%). Better diseasespecific survival in the NSS group was also observed in a study by Dash et al. (12) (83% vs. 73%), although the difference was not significant again.
In our study, the 5-year OS in the RN group was 71.2% compared with 83.1% in the NSS group; the 7-year OS was 63.1% and 64.4%, respectively, and the 12-year OS was 53.7% and 55.2%, respectively. CSS at 5 years was 80.9% and 97.1% in the RN and NSS groups, respectively; at 7 years, 76.4% and 80.6%; and at 12 years, 69.6% and 80.6%. The obtained findings are not exceptional compared with the findings on 5-year survival from the aforemen- Number  tioned studies, but our study is specific because it reported the data on 12-year survival.
when analyzing the outcomes of surgical treatment for RCC, several aspects have to be taken into consideration. Survival in the presence of RCC is known to be affected by patients' age, functional status, tumor size, histological type, G, and pT (7,8,(13)(14)(15)(16)(17)(18). Our Cox regression analysis also confirmed that in the presence of RCC measuring 4 to 7 cm, the aforementioned factors significantly influenced both OS and CSS independently of the type of surgery applied. while patients' age and concomitant diseases are known before surgery, and their effect on survival can be predicted, histological examination is possible only after surgery, and its effect on survival and the selection of the type of surgery is disputable. RCC 4 to 7 cm in size is attributed to clinical stage T1b, yet stage pT is frequently greater. Leibovich et al. (18) reported in their study that 20% of the patients in the RN group had stage pT3a and pT3b tumors, while tumors of this stage in the NSS group were detected in only 1% of cases. According to the researchers, this undoubtedly resulted in significantly poorer CSS following RN than NSS (85.9% and 98.3%, respectively). Mitchell et al. (19) indicated even a greater percentage of cases with stage ≥pT3 tumors in the presence of RCC measuring >4 cm (36.4% in the NSS group and 54.5% in the RN group). According to the authors, the estimated 5-year CSS was 96.2% in the NSS group and 97.8% in the RN group, while the type of surgery did not affect survival.
In our study, >pT1b tumors were detected in 40.2% of the subjects: in 14.7% of the subjects in the NSS group and in 42.3% of the patients in the RN group. In order to evaluate the effect of the surgical technique (NSS or RN) on survival, the subjects were divided into the groups pT1b, pT2, and ≥pT3 by the tumor stage. No significant differences in survival following the surgery of different types in the presence of RCC of different pathological stages were detected. we agree with other authors stating that NSS as a surgical technique ensures good longterm surgical results in the presence of RCC of various stages, when the tumor size is 4 to 7 cm.
Preoperative radiology does not always allow a precise evaluation of the malignancy of the renal tumor (20,21). Smaller tumors are more likely to be benign. The study by Frank et al. reported that the percentage of benign tumors decreased from 46.3% when the tumor size was <1 cm to 6.3% when the tumor size was 7 cm or more (22). Lesions measuring <4 cm are also more likely to be benign. weight et al. (23) indicated that among renal tumors measuring 4 to 7 cm, 20% of tumors following NSS and 10% of tumors following RN were found to be benign with the mean tumor size being 4.1 cm and 5.0 cm in the NSS and RN groups, respectively.
During the studied period, the percentage of benign tumors measuring 4 to 7 cm removed by applying the aforementioned surgical techniques in our institution was 5.6%.
When evaluating the significance of NSS in treating tumors >4 cm in size, the risk of relapse and multiple tumors should be taken into consideration. NSS is usually associated with a higher risk of relapse when compared with RN, but literature data are controversial. Patard et al. (8) in their study emphasized that RN was associated with a lower rate of local and systemic relapse if compared with NSS (0.6% and 2.3%). However, Mitchell et al. (19) reported that the surgical technique had no effect on relapse when treating RCC >4 cm in diameter. In the NSS and RN groups, 5-year survival was 93.5% and 83.3%, respectively. Antonelli et al. (24) in their study observed an unusually low rate of relapse in the NSS group (only 1.7%) when treating RCC measuring >4 cm (the mean postoperative followup was 72 months). we did not provide data on the time and the rate of relapse in our study, but we believe that the estimated 12-year CSS sufficiently reflects the risks of disease relapse and/or progression, which was lower in the NSS than in the RN group (80.6% vs. 69.6%).
The last but not least aspect in favor of NSS is preservation of the renal function. The rate of renal failure following NSS is lower than that observed after RN (25). Studies have demonstrated that glomerular filtration rate (GFR) is significantly better after NSS than RN. Mild (GFR <60 mL/min) or moderate (GFR <45 mL/min) renal failure was observed in 65% and 36% of the patients, respectively, who underwent RN compared with 20% and 5% of the patients, respectively, who underwent NSS (4). Preserved renal function is directly associated with better patients' quality of life and lower mortality associated with concomitant diseases. weight et al. (26) demonstrated that in the presence of renal tumors measuring 4 to 7 cm, renal failure developed after RN was associated with a 25% increased risk of cardiovascular mortality and a 17% increased risk of mortality related to other concomitant diseases as compared with NSS. Thompson et al. (27) reported that NSS reduced the risk of chronic renal failure, cardiovascular mortality, and the development of certain complications (hip fractures) compared with RN. Such postoperative results suggest that NSS could be used as the treatment of choice for RCC measuring 4 to 7 cm.
It is widely accepted that NSS is technically more complicated than RN. According to literature, the rate of complications following NSS is up to 33%, while the respective rate after RN is up to 10% (9,25). Our study showed that the rate of complications after NSS vs. RN was not different (8.8% vs. 6.6%, P=0.629), which suggests that this type of surgery is safe even in the presence of RCC measuring 4 to 7 cm.
Among the limitations of our study that might have influenced the results, one should mention the fact that the study was of a retrospective character, and the sample size of patients who underwent NSS was small. Besides, we did not evaluate either the time to relapse and its rate or the postoperative renal function. However, despite this, the evaluation of the short-term postoperative outcomes, when the mean follow-up is about 7 years and the overall 12year and cancer-specific survival is estimated, allow us to present certain generalized conclusions.

Conclusions
Our study showed that nephron-sparing surgery is a safe technique compared with radical nephrectomy that ensures good oncological control in the treatment of renal cell carcinoma measuring 4 to 7 cm and may be proposed as the treatment of choice for renal tumors not only up to 4 cm, but also 4 to 7 cm in size.

statement of Conflict of Interest
The authors state no conflict of interest.