Elsevier

European Urology

Volume 51, Issue 1, January 2007, Pages 112-120
European Urology

Prostate Cancer
A Nomogram for Staging of Exclusive Nonobturator Lymph Node Metastases in Men with Localized Prostate Cancer

https://doi.org/10.1016/j.eururo.2006.05.045Get rights and content

Abstract

Objectives

Some patients with localized prostate cancer are at risk of nonobturator lymph node invasion (NOLNI) and may require an extended pelvic lymph node dissection (ePLND). We explored the rate of exclusive NOLNI and developed a nomogram to predict it.

Material and methods

We mapped all ePLND specimens according to their anatomic location (obturator, external iliac, internal iliac lymph nodes) and assessed the location-specific rate of LNI in 565 patients. A multivariate logistic regression-based nomogram predicting NOLNI was then internally validated with 200 bootstrap resamples.

Results

Overall, 11.1% (63 of 565) had LNI and 21 (3.7%) had exclusive NOLNI. The nomogram predicting exclusive NOLNI was 80.2% accurate. The nomogram’s negative predictive value was 99%, when it predicted 0–10% probability of NOLNI. This approach could allow the omission of an ePLND in 350 of 565 (61.9%) patients and still correctly stage 85.8% of NOLNI cases.

Conclusions

Our nomogram-based approach offers the possibility of identifying men who are at virtually zero risk of exclusive NOLNI. In these men, an ePLND may be safely avoided.

Introduction

Pelvic lymphadenectomy (PLND) is as an essential staging procedure for patients treated with radical prostatectomy (RP) for localized prostate cancer [1]. Previous reports show that the prevalence of lymph node invasion (LNI) ranges from 1.1% to 26% [2], [3], [4], [5], [6], [7], [8]. Recent data suggest that more-extensive PLND might be necessary to detect occult LNI, because its prevalence might be directly related to PLND extent [2], [3], [4]. Indeed, a more-extensive PLND identifies metastases that would not be detected by limited dissections, because prostate cancer nodal metastases do not follow a predefined pathway of metastatic spread [9]. This observation was confirmed by several studies in which a limited PLND (lPLND) was associated with a high prevalence of false-negative findings [2], [3], [5], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18]. For example, Bader et al. [2] reported that up to 19% of patients with LNI may have metastases in the internal iliac distribution. Thus, a proportion of patients with LNI has extraobturator LNI and requires an LND that extends beyond the obturator fossa. An extended PLND (ePLND) should include the external iliac, internal iliac, and common iliac distributions. External iliac lymph node dissection is not of substantially greater complexity than that of the obturator LND. However, complete lymph node dissections from the internal iliac, common iliac, and presacral distributions may be of greater complexity. These landing zones represent a greater surgical challenge than the obturator and external iliac areas, and ePLNDs in these areas might be associated with a higher complication rate [19]. On the basis of this consideration, ePLNDs should be avoided in men who are at low risk of extraobturator LNI. Alternatively, those men in whom the risk of extraobturator LNI is non-negligible should be offered an ePLND. In this manuscript, we explored the rate of exclusive LNI outside of the obturator area, nonobturator LNI (NOLNI), and developed a tool capable of accurately predicting its probability.

Section snippets

Material and methods

RP and ePLND were performed in 608 patients between November 2002 and August 2005 at a single institution. Exclusions attributable to incomplete clinical information (16 for missing PSA and 27 for missing Gleason score) yielded 565 evaluable patients. Extended PLNDs consisted of excision of fibrofatty tissue along the external iliac vein, the distal limit being the deep circumflex vein and femoral canal. Proximally, ePLND was performed up to and included the bifurcation of the common iliac

Results

Patient age ranged from 45 to 82 yr (mean: 65.5). Clinical stages were T1c in 298 of 565 (52.8%) patients, T2 in 241 of 565 (42.6%), and T3 in 26 of 565 (4.6%). Biopsy Gleason sums (Table 1) were ≤6 in 358 patients (63.4%), 7 in 154 (27.2%), 8–10 in 53 (9.4%). Pretreatment PSA was 0.02–140 ng/ml (mean: 11.0; median: 7.19). The number of nodes removed ranged from 2 to 38 (mean: 17.5; median: 17). The median number of removed obturator lymph nodes was 9 (range: 1–28), while the median number of

Discussion

Several studies suggest that more-extensive PLND might be associated with a higher incidence of positive nodes [2], [3], [4], [5]. Extended PLND with a mean 17.8 lymph node count was associated with a threefold higher LNI rate versus modified PLND (mean: 9.3 removed lymph nodes; 23% vs 7%, p = 0.02) [5]. This finding was confirmed by Heidenreich et al. [3] and others [2]. However, the link between ePLND and the rate of LNI was not always confirmed [21]. Despite lack of unanimous agreement about

Conclusions

Of 565 men exposed to ePLND, 63 (11.1%) had LNI. Of those, 21 (3.7%) had exclusive NOLNI. Thus, it is clearly not justified to expose all 565 men to an ePLND. Our nomogram-based approach identifies men who are at virtually zero risk of NOLNI, in whom a staging ePLND may be safely avoided. The accuracy of our nomogram awaits external validation.

Editorial comment

Markus Graefen

[email protected]

In daily practice the majority of surgeons adapt their surgical approach regarding a pelvic

Acknowledgements

This study was partially supported by the Fonds de la Recherche en Santé du Québec, the Centre Hospitalier de l’Université de Montréal (CHUM)Foundation, the Department of Surgery, and Les Urologues Associés du CHUM (P.I.K.).

A.B. and F.K.-H.C. contributed equally to the manuscript.

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    It is also of note that three iterations of the Briganti nomogram for prediction of LNI have been published [6,23,24]. An additional nomogram, authored by Briganti et al. [8] was also authored to predict LNI outside of the obturator fossa and this nomogram is referenced in the NCCN PLND guideline. It is of note that this tool was never validated.

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