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Keywords:

  • SEER;
  • small renal mass;
  • surveillance;
  • ablation;
  • nephrectomy

Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

Study Type – Therapy (trend analysis)

Level of Evidence 2b

What's known on the subject? and What does the study add?

Treatment options for small renal masses include radical nephrectomy (RN), partial nephrectomy (PN), ablation, and surveillance. PN provides equivalent oncological as RN for small tumours, but long-term outcomes for ablation and surveillance are poorly defined. Due to changing techniques and technology, treatment patterns for small renal masses are rapidly developing. Prior studies had analysed utilisation trends for PN and RN to 2006, revealing a relative rise in the rate of PN. However, overall treatment trends including surveillance and ablation had not been studied using a population-based cohort.

It has become increasingly clear that RN is associated with greater renal and cardiovascular deterioration than nephron-sparing treatments. Thus, it is important to understand current population-based practice patterns for the treatment of small renal masses to assess whether practitioners are adhering to ever-changing principles in this field. The present study provides up-to-date treatment trends in the USA using a large population-based cohort.

OBJECTIVE

  • • 
    To describe the changing practice patterns in the management of small renal masses, including the use of surveillance and ablative techniques.

PATIENTS AND METHODS

  • • 
    All patients in the Surveillance, Epidemiology and End Results (SEER) registry treated for renal masses of ≤7 cm in diameter, from 1998 to 2008, were included for analysis.
  • • 
    Annual trends in the use of surveillance, ablation, partial nephrectomy (PN), and radical nephrectomy (RN) were calculated.
  • • 
    Multinomial logistic regression was used to determine the association of demographic and clinical characteristics with treatment method.

RESULTS

  • • 
    In all, 48 148 patients from 17 registry sites with a mean age of 63.4 years were included for analysis.
  • • 
    Between 1998 and 2008, for masses of <2 cm and 2.1–4 cm, there was a dramatic increase in the proportion of patients undergoing PN (31% vs 50%, 16% vs 33%, respectively) and ablation (1% vs 11%, 2% vs 9%, respectively).
  • • 
    In multivariable analysis, later year of diagnosis, male gender, being married, clinically localised disease, and smaller tumours were associated with increased use of PN vs RN. Later year of diagnosis, male gender, being unmarried, smaller tumour, and the presence of bilateral masses were associated with increased use of ablation and surveillance vs RN.

CONCLUSIONS

  • • 
    PN is now used in half of all patients with the smallest renal masses, and its use continues to increase over time.
  • • 
    Ablation and surveillance are less common overall, but there is increased usage over time in select populations.

Abbreviations
(R)(P)N

(radical) (partial) nephrectomy

CKD

chronic kidney disease

NCDB

National Cancer Data Base

SEER

Surveillance, Epidemiology, and End Results.

INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

The diagnosis of small renal masses is increasingly common [1], probably due to the detection of incidental masses during abdominal imaging. While radical nephrectomy (RN) has long been the standard of care, partial nephrectomy (PN) has been shown to yield equivalent oncological outcomes [2–4], and ablation represents an emerging, alternative nephron-sparing technology. Furthermore, there is growing evidence that some small renal masses may safely undergo an initial period of surveillance [5,6]. According to the most recent guidelines from the AUA, PN is the standard recommended treatment for all clinical T1a lesions and an alternate standard therapy for clinical T1b masses [7]. In contrast, indications for surveillance include older age, limited life expectancy, and the presence of comorbidities that would significantly increase risk if therapeutic intervention were undertaken [7]. Ablative therapies may be associated with decreased morbidity, but long-term oncological outcomes data are lacking.

When feasible, nephron-sparing approaches should be favoured considering data showing the increased risk of chronic kidney disease (CKD) after RN [8,9] as well as current understanding of the links between CKD and cardiovascular mortality [10,11]. However, separate investigators reviewing national data from 2001 [12], 2002 [13], and 2006 [14] concluded that PN remained under-utilised compared with RN. Notably, these investigators did not include surveillance or ablative therapies in their analyses. More recently, treatment trends through 2007 were assessed using the National Cancer Data Base (NCDB), which incorporates treatment at commission-accredited cancer programmes [15].

We queried the population-based Surveillance, Epidemiology, and End Results (SEER) database to assess nationwide practice patterns for the management of small renal masses, including the use of surveillance and ablation. Preoperative demographic and clinical features were examined for associations with treatment method.

PATIENTS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

Data was obtained from the SEER database, a USA population-based cancer registry managed by the National Cancer Institute. The SEER database includes incident cancer cases from 17 individual cancer registries, which mirror the demographic population of the USA and account for ≈28% of the USA population. Patients treated for benign tumours or who had non-diagnostic biopsies were not included in the database. Exemption was obtained from the Institutional Review Board for this analysis.

Adult (age >17 years) patients diagnosed and treated for renal cortical masses of ≤7 cm from 1998 to 2008 were identified in the SEER database. Non-parenchymal tumours, e.g. TCC, were excluded. Only participants accrued beginning in 1998 were included for analysis because this was the first year that ablative therapies were specifically recorded. Patient age, sex, ethnicity, marital status, treatment location, and year of diagnosis were abstracted. The pretreatment tumour size, presence of bilateral tumours, and treatment method were also recorded. SEER collects primary cancer-directed therapy within the first 4 months of diagnosis [16]. Surveillance was defined as no treatment within this window.

The chi-squared test was used to assess differences in baseline demographic and clinical characteristics between management strategies. Stacked bar graphs were created to further show the differences in management based on tumour size and year of diagnosis. Multinomial logistic regression was used to determine the independent association between baseline clinical variables and management strategy. The alpha value was set at 0.05 and 95% CIs were determined.

RESULTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

Between 1998 and 2008, 48 148 patients met the study criteria. In all, 30 626 (64%) underwent RN, 11 378 (24%) PN, 4426 (9%) ablation, and 1718 (4%) surveillance. The demographic and clinical characteristics for the entire cohort and for each treatment type are shown in Table 1, together with univariate analysis of the differences in each factor between treatment methods. The slight variation in subtotals for each characteristic reflects unrecorded data in the SEER database.

Table 1.  Clinical characteristics of patients diagnosed with renal cortical masses of ≤7 cm in the SEER database 1998–2008, stratified by treatment choice
CharacteristicRNPNAblationSurveillanceTotal
N (%) N (%) N (%) N (%) N (%) P *
  • *

    Chi-squared analysis was used to assess differences in clinical or pathological factors between treatment methods.

Age, years:      
 <505 023 (16.4)1 773 (15.6)282 (16.4)684 (15.5)7 762 (16.1)0.26
 50–596 838 (22.3)2 644 (23.2)399 (23.2)1 006 (22.7)10 887 (22.6)
 60–698 066 (26.3)3 014 (26.5)439 (25.6)1 124 (25.4)12 643 (26.3)
 70–796 964 (22.7)2 573 (22.6)379 (22.1)1 067 (24.1)10 983 (22.8)
 >803 734 (12.3)1 374 (12.1)219 (12.7)545 (12.3)5 872 (12.2)
Sex:      
 Female12 342 (40.3)4 165 (36.6)656 (38.2)1 725 (38.9)18 888 (39.2)<0.01
 Male18 284 (59.7)7 213 (63.4)1 062 (61.8)2 701 (61.1)29 260 (60.8)
Ethnicity:      
 Caucasian22 714 (74.6)8 554 (75.9)1 343 (78.6)3 172 (71.8)35 783 (74.8)<0.01
 African–American3 196 (10.5)1 170 (10.4)150 (8.8)615 (13.8)5 131 (10.7)
 Latino2 952 (9.7)967 (8.6)136 (7.9)422 (9.6)4 477 (9.4)
 Asian/Other1 575 (5.2)582 (5.2)80 (4.7)211 (4.8)2 448 (5.1)
Marital status:      
 Married19 428 (63.4)7 558 (66.4)1 048 (61.0)2 093 (50.1)30 127 (62.6)<0.01
 Unmarried11 198 (36.6)3 820 (33.6)670 (39.0)2 333 (47.3)18 021 (37.4)
Tumour size, cm:      
 <23 198 (10.4)3 818 (33.6)484 (28.2)815 (18.4)8 315 (17.3)<0.01
 2.1–413 441 (43.9)5 943 (52.2)1 097 (63.9)1 898 (42.9)22 379 (46.5)
 4.1–713 987 (45.7)1 617 (14.2)137 (8.0)1 713 (38.7)17 454 (36.2)
SEER stage:      
 Localised30 067 (98.2)11 314 (99.4)1 707 (99.4)3 468 (78.4)46 556 (96.7)<0.01
 Regional210 (0.7)14 (0.1)0 (0)96 (2.2)320 (0.6)
 Distant349 (1.1)50 (0.5)11 (0.6)862 (19.4)1 272 (2.7)
Residence:      
 Rural1 641 (5.4)528 (4.7)61 (3.6)260 (5.2)2 490 (5.9)<0.01
 Near metropolitan1 935 (6.4)586 (5.2)104 (6.1)292 (6.7)2 917 (6.1)
 Metropolitan26 852 (88.2)10 203 (90.1)1 544 (90.3)3 839 (87.1)42 438 (88.0)

Overall trends in treatment method are shown in Fig. 1 and stratified by tumour size in Fig. 2. Between 1998 and 2008, there was a steady rise in the use of PN, representing 30% of all patients in 2008. While RN remained the most common treatment, the use of ablation and surveillance represented 7% and 11% of the cohort in 2008, respectively. For masses of ≤2 cm and 2.1–4 cm in diameter, there was a dramatic increase in the proportion of patients undergoing PN (31% vs 50%, P < 0.001 and 16% vs 33%, P < 0.001, respectively) and ablation (1% vs 11%, P < 0.001 and 2% vs 9%, P < 0.001, respectively).

image

Figure 1. Overall trends in treatment choice for renal cortical masses of ≤7 cm from 1998 to 2008. PN, ablation, and surveillance have become increasingly common in recent years, representing 30%, 7%, and 11% in 2008, respectively.

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image

Figure 2. Trends in RN, PN, ablation, and surveillance for renal cortical masses stratified by tumour size.

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The associations of demographic and clinical variables with the likelihood of undergoing PN, ablation, or surveillance relative to RN were assessed using multivariate analysis, and the results are shown in Table 2. Later year of diagnosis, male gender, being married, clinically localised disease, and smaller tumours were associated with increased use of PN vs RN. Later year of diagnosis, male gender, being unmarried, smaller tumours, and the presence of bilateral masses were associated with increased use of ablation and surveillance vs RN. Patient age at diagnosis did not show a consistent effect on treatment choice when analysed as a categorical or a continuous variable (data not shown). The effect of SEER registry and region on treatment method were investigated and were not statistically significant with multivariate analysis.

Table 2.  Multinomial logistic regression analysis showing the effect of each clinical characteristic on the relative likelihood of undergoing each treatment type vs RN
Characteristic(referent group)PNAblationSurveillance
RR (95% CI) P RR (95% CI) P RR (95% CI) P
  1. RR, relative risk.

Age, years (<50):      
 50–591.11 (1.02–1.19)0.011.03 (0.88–1.22)0.691.04 (0.93–1.16)0.51
 60–691.07 (0.99–1.15)0.070.97 (0.83–1.14)0.751.00 (0.89–1.11)0.97
 70–791.10 (1.02–1.19)0.011.05 (0.89–1.24)0.571.07 (0.96–1.20)0.21
 >801.07 (0.98–1.17)0.141.09 (0.91–1.32)0.351.04 (0.91–1.18)0.57
Gender (female):      
 Male1.16 (1.10–1.22)<0.0011.14 (1.02–1.27)0.021.20 (1.11–1.30)<0.001
Ethnicity (Caucasian):      
 African-American0.96 (0.88–1.04)0.310.69 (0.57–0.83)<0.0011.29 (1.16–1.45)<0.001
 Latino0.85 (0.78–0.93)<0.0010.75 (0.61–0.91)0.0031.05 (0.92–1.19)0.45
 Asian/Other0.88 (0.78–0.99)0.040.94 (0.72–1.22)0.620.95 (0.79–1.15)0.61
Marital status (unmarried):      
 Married1.10 (1.04–1.16)<0.0010.87 (0.78–0.97)0.010.48 (0.44–0.51)<0.001
Tumour size, cm (<2):      
 2.1–40.38 (0.36–0.40)<0.0010.56 (0.50–0.64)<0.0010.55 (0.50–0.61)<0.001
 4.1–70.10 (0.09–0.11)<0.0010.07 (0.06–0.09)<0.0010.39 (0.35–0.43)<0.001
Laterality (unilateral):      
 Bilateral1.24 (0.51–3.04)0.643.92 (1.08–14.24)0.046.89 (3.18–14.93)<0.001
SEER stage (localized):      
 Regional0.28 (0.16–0.49)<0.001<0.01 (0–0.01)0.984.61 (3.55–5.99)<0.001
 Distant0.51 (0.37–0.69)<0.0010.55 (0.28–1.08)0.0825.36 (21.98–29.25)<0.001
Residence (rural):      
 Near metropolitan area0.89 (0.76–1.03)0.131.12 (0.77–1.61)0.560.89 (0.71–1.09)0.27
 Metropolitan area1.01 (0.89–1.15)0.851.05 (0.76–1.44)0.780.85 (0.71–1.01)0.07
Year of diagnosis (1998):      
 19991.18 (0.95–1.48)0.140.06 (0.01–0.47)0.011.23 (0.90–1.69)0.20
 20001.50 (1.24–1.82)<0.0010.57 (0.29–1.14)0.111.33 (1.00–1.75)0.05
 20011.53 (1.26–1.85)<0.0010.93 (0.51–1.71)0.831.60 (1.22–2.10)0.001
 20021.89 (1.57–2.27)<0.0011.03 (0.57–1.87)0.911.64 (1.25–2.14)<0.001
 20032.19 (1.83–2.63)<0.0012.06 (1.19–3.57)0.011.57 (1.19–2.05)<0.001
 20042.59 (2.17–3.11)<0.0014.03 (2.38–6.81)<0.0012.02 (1.55–2.62)<0.001
 20052.59 (2.17–3.11)<0.0015.07 (3.01–8.52)<0.0012.01 (1.55–2.61)<0.001
 20062.96 (2.48–3.54)<0.0017.23 (4.32–12.09)<0.0012.07 (1.59–2.68)<0.001
 20073.45 (2.89–4.12)<0.0018.48 (5.08–14.16)<0.0012.44 (1.89–3.15)<0.001
 20083.91 (3.28–4.66)<0.00111.24 (6.75–8.71)<0.0012.59 (2.01–3.35)<0.001

DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES

The management of small renal masses is rapidly developing, as familiarity with novel technology and operative technique becomes more pervasive. A growing body of data supports renal-preserving therapy whenever feasible [8,10,11]. We reviewed a large representative nationwide database of patients diagnosed with small renal masses to track practice patterns over time. We report a continued rise in the use of PN, representing the treatment of choice in 30% of all T1 renal masses and 50% of masses of ≤2 cm in 2008. PN was associated with male gender, married status, clinically localised disease, and smaller tumours. We are the first to describe nationwide rates of surveillance and ablation in a population-based database, representing 11% and 7% of the cohort in 2008, respectively. Male gender, older age, smaller tumours, and bilateral masses were associated with surveillance and ablation.

The present data reflect a significantly higher rate of PN vs RN over time, especially for the smallest renal cortical masses. This represents a significant improvement from prior studies [12,13] but probably still reflects underuse of nephron-sparing techniques. There is growing data to indicate that RN is associated with worse renal function than PN [8,9,11], and it has been shown that incremental decrease in renal function is associated with increased risk of death and cardiovascular events [10]. Weight et al. [11] (2010) reported an excess loss of 25% of renal function in patients undergoing RN vs PN, and this difference was linked to increased cardiovascular and all-cause mortality. The renal function advantage of nephron-sparing surgery over RN persists even with extended ischaemia intervals of >30 min [9]. Such evidence, together with equivalent oncological outcomes of PNcompared with RN [17,18], argue convincingly that a nephron-sparing approach should be used whenever possible for T1 renal cortical masses. Greater surgeon awareness of this evidence as well as continued urologists' training in alternatives to RN are crucial.

However, PN is not always possible. Anatomical considerations, e.g. proximity of the mass to the renal hilum, central tumour location, or adhesions from prior abdominal surgery, may preclude nephron-sparing excision. Also, while overall complication rates remain low, there are higher reported rates of complications for PN vs RN. In a review of 541 patients undergoing elective open PN and RN, Van Poppel et al. [19] found that patients undergoing open nephron-sparing excision had higher rates of severe haemorrhage (3.1% vs 1.2%), urinary fistulae (4.4% vs 0%), and need for re-operation for complications (4.4% vs 2.4%). Given these considerations, not all patients are candidates for a nephron-sparing approach, and some may not choose this approach after informed discussion. Thus, while current practice patterns seem to reflect overuse of RN for small masses, the optimal usage rate is difficult to assess. Future research incorporating documentation of the rationale for therapeutic approach is necessary to make this assessment.

To our knowledge, only one other study has assessed broad usage rates of ablation and surveillance, using the NCDB [15]. The proportion of patients undergoing ablation in 2007 in the present cohort (6%) was similar to that in the NCDB (6.8%), with a comparable rate of increase since 1998. However, rates of surveillance in 2007 differ significantly (SEER 11% vs NCDB 3.3%). This is probably because the NCDB includes only hospitals accredited by the Commission on Cancer, while SEER is a population-based cohort. Commission-accredited hospitals represent higher volume treatment centres and may favour extirpative treatment over surveillance due to greater familiarity with operative approaches.

As with PN, it is similarly difficult to determine the optimal rate of use for surveillance and ablation. Currently, indications for surveillance include elderly age, poor life expectancy, and undue surgical risk due to comorbidities [7]. The role of ablation is still being defined. Although ablation may offer lower associated morbidity, its oncological efficacy awaits validation before it can be recommended for widespread use for small renal masses that are otherwise highly curable. Until then, it is not surprising that ablation and surveillance were associated with patients having smaller masses, which are more likely to be benign. That patients with bilateral masses were also more likely to undergo ablation and surveillance probably reflects a perception that these treatment methods maximise renal function after treatment.

Surprisingly, patient age at diagnosis was not consistently associated with use of PN, ablation, or surveillance, even though it is listed as an indication for surveillance in the most recent AUA clinical guideline [7]. Younger patient age in all categories was previously found to be a significant predictor for PN in nationwide databases of 2001 [12] and 2002 [13]. More recently, when tracking data during 2006, age of <50 years was only associated with PN when compared with patients aged >70 years [14]. It was presumed that PN was a more morbid procedure preferentially used by younger patients. That the present analysis does not show patient age as a consistent predictor of treatment choice probably reflects growing surgeon familiarity and comfort with PN, making physicians more able to counsel patients from all age groups similarly. Alternatively, considering the growing evidence of the harms of CKD, urologists may be realising that older patients with worse renal function have the most to gain from nephron-sparing surgery.

The present finding that married patients were more likely to undergo PN vs RN is consistent with others' recent findings. Married patients were more likely than single patients to choose surgical intervention when confronted with metastatic RCC [20] or RCC with venous tumour thrombus [21]. It was proposed that married status may reflect stronger social support and thus a greater willingness to undergo aggressive surgery. PN, which carries a higher rate of postoperative haemorrhage and complications [19], is similarly favoured by married patients in the present cohort.

In the present cohort there was also adistinct gender discrepancy in treatment use. Men were significantly more likely to undergo PN, surveillance, and ablation, while women were more likely to undergo RN. Others have also reported men to preferentially undergo PN over RN [12–14], and the present findings about surveillance and ablation agree with the only other study to assess these outcomes [15]. In studies comparing solely RN and PN, proposed explanations for the gender disparity included patient driven female preference for less risky procedures [14], as well as the finding that women are more likely to have benign or complex cystic tumours on radiographic imaging, which may influence women to choose surveillance rather than surgical extirpation [14,22]. The present finding that men are more likely to choose surveillance and ablation argues against both of these theories. Instead, the gender discrepancy is more likely to be due to greater recognition of CKD in men due to their higher baseline serum creatinine levels. Others have found that both patients and physicians exhibit a greater awareness of CKD in men compared with women [23–25], and during patient counselling about small renal masses, this may confer a preference for nephron-sparing treatment in men.

There are limitations of the present analysis. The SEER database does not include information about certain factors that affect treatment choice, such as medical comorbidities, location of the renal mass within the kidney, and intraoperative findings that may affect surgical plan. As noted, the SEER database is a cancer registry and excludes patients with known benign tumours or who underwent non-diagnostic biopsies. Thus, true utilisation rates for nephron-sparing techniques may be underestimated. However, we expect that excluded patients represent a small proportion of the overall cohort, and this analysis accurately assesses treatment trends for malignant lesions. The definition of surveillance as a lack of treatment within 4 months of diagnosis may overestimate the true rate of surveillance, as some of these patients may have other reasons for delay in treatment. However, given that there is no consensus definition for surveillance and that >90% of the present cohort did undergo treatment within 4 months, we think the present data provides a reasonable measure of nationwide surveillance. As noted earlier, there is insufficient data to determine the optimal usage rate for PN, ablation, or surveillance. While these current practice patterns seem to reflect overuse of RN for small renal masses, future research including documented treatment rationale is needed. Despite these limitations, this analysis provides up-to-date nationwide practice patterns on which to base on-going efforts to optimise the management of increasingly common small renal masses.

In conclusion, PN is now used in half of all patients with the smallest renal masses, and its use continues to increase over time. Ablation and surveillance are less common overall, but there is increased usage over time in men, unmarried patients, and those with small or bilateral tumours.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. PATIENTS AND METHODS
  5. RESULTS
  6. DISCUSSION
  7. CONFLICT OF INTEREST
  8. REFERENCES