Pelvic Lymph Node Dissection in Prostate Cancer for metastasis (60%) was the obturator fossa. Overall, how- ever, 58% and 36% of the patients had deposits in the in- ternal iliac and external iliac nodal areas, respectively, whereas 19% had positive nodes distributed in the internal iliac vessels alone. Thus, if pelvic lymphadenectomy was confined to the obturator fossa, it would miss approx- imately 60% of the metastases, because most of the histo- pathologically proven metastatic LNs were found in the ex- ternal and internal iliac node packets. Similar results were reported in a study that compared a historical series of pa- tients who underwent lPLND with a contemporary series who underwent ePLND. That study reported that 42% of positive nodes were located outside the limited template [28,31]. Moreover, the authors determined that 25% of all positive LNs were exclusively located in the area around the internal iliac artery. 　With respect to primary lymphatic landing sites, Mattei et al mapped the prostatic nodal landing zones by injecting Tc-99-labeled colloid into patients’ prostates [35]. They found that, even by using the extended template, approx- imately one-third of the primary landing sites would still be missed and advocated including the tissue along the common iliac vessels up to the crossing of the ureter. For accurate staging including all primary lymphatic draining sites, the field of LN dissection should theoretically include tissue up to the origin of the inferior mesenteric artery. 　In contrast, Clark et al performed a prospective random- ized evaluation of 123 patients undergoing radical prosta- tectomy to assess the diagnostic value of an ePLND involv- ing the presacral area compared with sPLND for detecting nodal metastasis [30]. On the basis of eight patients in whom LN metastasis was confirmed histopathologically, they concluded that ePLND did not improve the accuracy of LN staging compared with sPLND. This is the only study to date that was designed to be prospective and random- ized; however, the majority of the patients presented with low-risk prostate cancer with a low rate of LNI. Further- more, ePLND was performed on only one side, and no data were given regarding the number of LNs removed from each group. 　To measure the exact LN yield following PLND, an addi- tional factor to consider is the pathological examination method. In bladder cancer studies, greater nodal yields have been noted when lymphadenectomy specimens are sent as separate packets (such as external iliac and ob- turator) rather than en bloc [36,37]. Separate examination of specimens is an important procedure for optimizing LN detection and provides an accurate determination of nodal tumor burden [36,38]. 　In summary, more extensive dissection results in in- creased LN yield. As more nodes are removed, more pos- itive nodes are found and fewer positive nodes are missed. For more accurate staging and a possible cure for minimal nodal disease, more extensive PLND could be used. However, based on the knowledge of primary lymphatic landing sites, many lymph nodes would still be missed even with ePLND. 439 FOR WHICH PATIENTS IS PLND NECESSARY? After the introduction of PSA testing, the rate of LNI dra- matically decreased to about 4% to 6% [7,8]. In Korea, the reported incidence of LNI by sPLND is between 4% and 6%. Kim et al reviewed their experience with 1,324 radical pros- tatectomy cases and reported that that 6% of patients had LNI [39]. Ham et al investigated 273 patients who under- went robotic prostatectomy. Among them, 11 patients (4%) showed LNI [40]. In our institution, of 351 patients who un- derwent limited or standard PLND, LNI was determined in 20 (5.7%) patients (unpublished data). With lower rates of pelvic LN metastasis [7,8] and the potential complica- tions that can develop after PLND [30,41], knowing which prostate cancer patients need to undergo PLND regret- tably remains undetermined. Several nomograms have been designed to predict LNI (Table 1) and to identify pa- tients who may derive the most benefit from PLND [10-15, 42-51]. Most nomograms, including the well-known Partin tables [12,52] and Memorial Sloan-Kettering nomograms [42], predict pathologic stage by using preoperative clinical stage, biopsy Gleason scores, and preoperative PSA levels [12-14,42,53,54]. However, although these nomograms are well established and are certainly useful for the clinical de- cision making process, the predictive ability of most nomo- grams, except for two, is limited by the data used to create them. Most datawere obtained from series of lPLND with a mean of 6 to 9 LNs removed (Table 1) [10-15,42-52]. Therefore, the true prevalence of LNI may be significantly underestimated owing to the limited nodal sampling. Heidenreich et al compared 103 patients who underwent ePLND with 100 patients who received only sPLND in which no significant differences in age, preoperative PSA levels, or mean biopsy Gleason scores existed [31]. They re- ported that ePLND was associated with a high rate of LN metastasis outside of the fields of sPLND in cases of clin- ically localized prostate cancer [31]. Similarly, other stud- ies also found that nomograms based on sPLND, where in- ternal iliac nodes were not sampled, could not be considered a reliable method because sPLND could miss 25% to 50% of the positive nodes compared with extended dissection [31,32,53,55,56]. 　A Korean multi-institutional study developed a nomo- gram to predict LNI [57]. But, the nomogram was also based on sPLND and so could only predict the pathological stage of the clinically localized prostate cancer. To over- come this limitation, Briganti et al created and validated a nomogram that estimates the optimal number of nodes that should be removed based on clinical parameters and the number of nodes removed during ePLND [53,55]. From internal validation with 602 patients, their nomogram demonstrated an accuracy of 76% based on ePLND [53]. Within the same groups of risk from the D’Amico classi- fication system [58], significantly higher LNI predictions using the Brigantin nomogram are likely, in part due to the ePLND data used to generate them. However, its reli- ability may be decreased by the fact that the majority of pa- Korean J Urol 2011;52:437-445