Optimal assessment of lymph node status in gallbladder cancer

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ScienceDirect EJSO 42 (2016) 205e210

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Optimal assessment of lymph node status in gallbladder cancer S.H. Kim a, J.U. Chong b, J.H. Lim c, G.H. Choi b, C.M. Kang b, J.S. Choi b, W.J. Lee b, K.S. Kim b,* a

Department of Surgery, Yonsei University Wonju College of Medicine, Wonju Severance Christian Hospital, Wonju, Republic of Korea b Department of Surgery, Yonsei University College of Medicine, Yonsei University Health System, Seoul, Republic of Korea c Department of Surgery, Yonsei University College of Medicine, Yongin Severance Hospital, Yongin, Republic of Korea Accepted 29 October 2015 Available online 14 November 2015

Abstract Background: Lymph node (LN) metastasis is an important prognostic factor in gallbladder cancer (GBCA). LN status has been adopted as a critical element of staging systems. However, the influence of total lymph node count (TLNC) remains unclear. We determined the optimal minimum TLNC and compared the prognostic significance of LN status indices in GBCA. Methods: We retrospectively reviewed medical records of 128 patients with T2 or greater GBCA who underwent LN dissection. We analyzed overall survival (OS) and relevance of the number of metastatic LNs, ratio of metastatic LNs to retrieved LNs (LNR), and TLNC in predicting OS. Results: The median OS durations were 120, 35, and 18 months in T2, T3, and T4 GBCA. Five-year OS rates were 73%, 43%, and 0% in T2, T3, and T4 GBCA. LN status did not significantly impact OS in T2 or T4 GBCA. However, all LN indices were significantly correlated with OS in T3 GBCA. Furthermore, multivariate analysis revealed that a metastatic LN count of more than four and a TLNC of more than eight were independent prognostic factors of OS in T3 GBCA. Conclusions: TLNC and the number of positive LNs may be more important prognostic factors than LNR in T3 GBCA. Additionally, accurate staging may not be achieved in cases of T3 GBCA if the total number of retrieved LNs is less than eight. Thus, to ensure proper staging, we recommend that surgeons harvest more than eight LNs in patients with T3 GBCA. Ó 2015 Elsevier Ltd. All rights reserved.

Keywords: Gallbladder cancer; Overall survival; Lymph node

Introduction Gallbladder cancer (GBCA) is a rare malignancy with distinct racial and geographic distributions.1 GBCA is the most common biliary tract tumor, which has a dismal prognosis, especially in its advanced stages.2e4 Among several prognostic factors, tumor invasion depth is an important prognostic factor in GBCA.2,5 Recently, the * Corresponding author. Department of Surgery, Yonsei University College of Medicine, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Republic of Korea. Tel.: þ82 2 2228 2125; fax: þ82 2 313 8289. E-mail address: [email protected] (K.S. Kim). http://dx.doi.org/10.1016/j.ejso.2015.10.013 0748-7983/Ó 2015 Elsevier Ltd. All rights reserved.

incidence of early GBCA has increased because of the use of laparoscopy for treating gallbladder disease.6,7 Patients with T1 and T2 GBCA have exhibited improved survival, but those with advanced GBCA still have a poor prognosis, despite the use of laparoscopy.8,9 In addition to tumor invasion depth, nodal disease status is another important prognostic factor in GBCA. Specifically, patients with lymph node (LN) metastases have a poor prognosis.10,11 However, the effect of nodal disease status is still unclear. The concept of nodal disease status has changed with the updates from the 5th American Joint Cancer Committee (AJCC) staging system to the 7th AJCC staging system. The 6th AJCC staging system classified

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patients into LN-negative or LN-positive groups.12 In contrast, the 7th AJCC staging system classified patients into three groups according to the site of LN metastases.13 Some studies reported that the number of LN metastases was more important than the location of the LN metastases,11,14 while other studies emphasized the importance of LN ratio in hepatobiliary cancers, including gallbladder cancer.15e17 Additionally, a consensus has not been reached regarding the influence of the total lymph node count (TLNC) on GBCA prognosis. The 6th AJCC staging system recommended that surgeons evaluate at least three LNs. However, the 7th AJCC staging system did not make any recommendations regarding the minimum TLNC. Accordingly, the importance of each LN status index remains a subject of debate. Many previous study results were obtained in the context of LN counts less than six. However, these low LN counts can distort the value of using the number of metastatic LNs as a prognostic tool by undercounting. Also, low LN counts can affect the accuracy of using LNR by overweighting.18 In this study, we determined the minimum TLNC that best predicted overall survival (OS) in GBCA, and compared the prognostic significance of TLNC to other LN indices, including the number of positive LNs and LN ratio. Patients and methods Patients Between January 2000 and December 2009, 156 patients with T2 or greater GBCA underwent surgical resection with curative intent at the Severance Hospital, Yonsei University Health System, Seoul, Korea. We excluded 28 patients who did not undergo LN dissection. Overall, we included a total of 128 patients who underwent R0, R1, or R2 resections with curative intent. Their medical records were retrospectively reviewed. Definition of lymph node dissection LN dissection was classified as either D1 or D2 dissection. D1 was defined as dissection around the hepatoduodenal ligament (including LN removal around the cystic duct, bile duct, portal vein, and hepatic artery) and dissection of LNs around the gastrohepatic ligament. D2 dissection was defined as D1 dissection plus dissection of the celiac LNs, pancreaticoduodenal LNs, and para-aortic LNs (areas above and below the renal vein). Surgical strategy and adjuvant treatment Five surgeons performed radical cholecystectomies during the study period. All surgeons performed the D2 dissections early in the study period. After 2007, three surgeons

performed primarily D1 dissections because of the dismal prognosis of patients with N2 disease. They evaluated the status of para-aortic LNs via inspection and palpation intraoperatively and performed D2 dissections only when metastasis to these LNs was suspected. Many patients with T3, N1, or greater disease received adjuvant chemotherapy, radiotherapy, or chemoradiation therapy. Patients were referred to medical oncologists, and each oncologist chose different agents. Adjuvant therapy was not performed if patients refused or if their performance status was greater than two based on the Eastern Cooperative Oncology Group guidelines. Parameters of nodal disease We evaluated previous study results that explored the parameters of nodal disease. Sakata et al. reported that more than four positive LNs were prognostically significant.11 In addition, Negi et al. reported that the ratio of metastatic LNs to retrieved LNs (LNR) was a prognostic factor for OS.16 To further clarify this issue, we evaluated the optimal TLNC in this study. Outcomes We analyzed patient disease-free survival and overall survival (OS), and evaluated prognostic factors of OS in patients with T2 or greater GBCA. In particular, we evaluated the associations between parameters of nodal disease and OS. We performed subgroup analyses according to the tumor invasion depth in order to identify whether parameters of nodal disease were associated with OS in these subgroups. Statistical analysis Statistical analysis was performed with SPSS version 15.0 software (SPSS Inc., Chicago, IL, USA). Results for all continuous data are presented as the median (range). Results for all categorical data are presented as numbers and percentages. OS and DFS were calculated using the KaplaneMeier method. Univariate and multivariate analyses of OS were conducted using Cox’s proportional hazard model (forward stepwise) to identify prognostic factors. Statistical significance was defined as a p-value <0.05. Results Baseline characteristics A total of 128 patients with stage T2 or greater GBCA underwent LN dissection. Patient baseline characteristics are presented in Table 1. The median patient age was 61 years. Seventy-six (59.4%) patients were female. Twentysix (20.3%) patients were diagnosed with GBCA after laparoscopic cholecystectomy. Twenty patients (15.6%) were

S.H. Kim et al. / EJSO 42 (2016) 205e210 Table 1 Baseline patient characteristics (N ¼ 128). Variable Age (years) Gender CA 19-9 (U/mL) Previous cholecystectomy Lymph node dissection Extent of resection

Tumor differentiation

Lymphovascular invasion Perineural invasion No. retrieved LNs No. positive LNs Tumor invasion depth

Node involvement

7th AJCC stage

207

The 5-year OS rates were 68%, 55%, and 0% in N0, N1, and N2 GBCA. Median (range) or n (%)

Female Male No Yes D1 D2 R0 R1 R2 WD MD PD No Yes No Yes

T2 T3 T4 N0 N1 N2 II IIIA IIIB IVA IVB

61 76 52 14.9 102 26 50 78 100 20 8 32 57 28 97 31 102 26 11 1 60 60 8 59 55 14 35 17 46 5 25

(29e79) (59.4%) (40.6%) (0e20,000) (79.7%) (20.3%) (39.1%) (60.9%) (78.1%) (15.6%) (6.3%) (27.4%) (48.7%) (23.9%) (75.8%) (24.2%) (79.7%) (20.3%) (1e60) (0e33) (46.9%) (46.9%) (6.3%) (46.1%) (43%) (10.9%) (27.3%) (13.3%) (35.9%) (3.9%) (19.5%)

AJCC, American Joint Committee on Cancer; CA, carbohydrate antigen; MD, moderate differentiation; No, number; PD, poor differentiation; WD, well-differentiated.

found to have positive resection margins on permanent pathologic examination, and eight (6.3%) underwent palliative surgery. Sixty patients had T2 GBCA, 60 had T3 GBCA, and eight had T4 GBCA. Sixty-nine (53.9%) patients exhibited node metastasis. The median TLNC was 11, and the median number of positive LNs was one.

Prognostic factors among lymph node parameters According to univariate analysis, carbohydro antigen (CA) 19-9 levels greater than 37 U/mL, the extent of resection, the use of adjuvant therapy, tumor differentiation, lymphovascular invasion (LVI), perineural invasion (PNI), tumor invasion depth, node involvement, number of positive LNs, and LNR were significant prognostic factors of OS. However, multivariate analysis revealed only the use of adjuvant therapy ( p ¼ 0.029; hazard ratio [HR] 2.562; 95% confidence interval [CI] 1.103e5.951), tumor invasion depth (T4 vs T2: p ¼ 0.005; HR 5.573; 95% CI 1.66e18.712), greater than four positive LNs ( p ¼ 0.011; HR 3.016; 95% CI 1.284e7.085), and LNR ( p ¼ 0.002; HR 4.181; 95% CI 1.695e10.311) to be independent prognostic factors. Thus, among the LN parameters, positive LN number and LNR were prognostic factors for the OS (Table 2). Notably, the extent of liver resection and bile duct resection were not found to be prognostic factors. In addition to the above analyses, we also performed subgroup analysis according to the tumor invasion depth. LN parameters were not significantly different among patients with T2 and T4 GBCA (data not shown). As shown in Fig. 1, all parameters were significant predictors of OS in patients with T3 GBCA. In these patients, CA 19-9, the extent of resection, lymphovascular invasion (LVI), node involvement, number of retrieved LNs, number of positive LNs, and LNR were identified as prognostic factors according to the univariate analysis. However, multivariate analysis showed only LVI ( p ¼ 0.033; HR 2.503; 95% CI 1.077e5.815), a TLNC greater than eight ( p < 0.001; HR 0.114; 95% CI 0.04e0.32), and more than four positive LNs ( p < 0.001; HR 16.4; 95% CI 5.196e51.757) to be independent prognostic factors (Table 3). Discussion

Surgical outcomes Among 60 patients with T2 GBCA, 25 patients received adjuvant therapy (17 of whom had LN metastases). Among 60 patients with T3 GBCA, 46 received adjuvant therapy (32 of whom had LN metastases). Among eight patients with T4 GBCA, only three received adjuvant therapy (two of whom had LN metastases). Seventy-four patients (50.7%) experienced recurrence during a median 25-month (range: 1e127 months) follow-up period. The median OS duration was 120, 35, and 18 months for T2, T3, and T4 GBCA, respectively. The 5-year OS rates were 73%, 43%, and 0% in T2, T3, and T4 GBCA, respectively. The median OS was 108, 96, and 11 months in N0, N1, and N2 GBCA, respectively.

The status of LN metastasis has been defined differently among the 5th, 6th, and 7th AJCC TNM staging systems.12,13 Many studies have evaluated whether the location of LN metastases, extent of LN dissection, or LNR are significant prognostic factors of OS in GBCA.5,9,11,14,16,19 However, the number of retrieved LNs was not fully evaluated in these studies. Recently, Ito et al.15 reported on what characterizes an adequate LN assessment for extrahepatic bile duct adenocarcinoma. However, they did not include GBCA in their evaluation. In our study, we found that the number of retrieved LNs and the number of metastatic LNs were more important prognostic factors than the LNR. In particular, we found that retrieving eight LNs in patients with T3 GBCA was prognostically significant.

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Table 2 Univariate and multivariate analysis of overall survival in all patients. Variable

CA 19-9 (U/mL) Previous cholecystectomy LN dissection CBD resection Liver resection Extent of resection Adjuvant therapy Tumor differentiation Lymphovascular invasion Perineural invasion Tumor invasion depth Node involvement No. retrieved LNs No. positive LNs LNR

Univariate analysis 37 Yes D2a Yes Yes R1 R2 Yes MD vs. WD PD vs. WD Yes Yes T3 vs. T2 T4 vs. T2 N1 vs. N0 N2 vs. N0 8 4 0.5

Multivariate analysis

HR

p

95% CI

3.263 0.373 0.655 1.138 1.143 3.121 9.583 2.369 2.189 3.789 2.756 2.12 3.323 9.589 1.567 5.106 0.79 5.389 5.787

<0.001 0.06 0.152 0.667 0.666 0.001 <0.001 0.004 0.089 0.007 0.001 0.023 0.001 <0.001 0.181 <0.001 0.397 <0.001 <0.001

1.758e6.056 0.134e1.041 0.367e1.169 0.632e2.048 0.623e2.099 1.572e6.198 4.197e21.878 1.313e4.274 0.888e5.4 1.437e9.992 1.512e5.023 1.109e4.05 1.69e6.534 3.307e27.805 0.811e3.028 2.27e11.486 0.458e1.363 2.728e10.644 2.933e11.419

HR

p

95% CI

2.562

0.029

1.103e5.951

2.229 5.573

0.057 0.005

0.978e5.08 1.66e18.712

3.016 4.181

0.011 0.002

1.284e7.085 1.695e10.311

AJCC, American Joint Committee on Cancer; CA, carbohydrate antigen; CBD, common bile duct; CI, confidence interval; HR, hazard ratio; LN, lymph node; LNR, metastatic to retrieved lymph node ratio; MD, moderate differentiation; No, number; OS, overall survival; PD, poor differentiation; WD, well-differentiated. a D2 dissection includes dissection of lymph nodes around the hepatoduodenal and gastrohepatic ligaments and in the para-aortic areas.

LN status is a critical factor in patients with GBCA. The number of metastatic LNs and LNR were evaluated as prognostic factors in several previous studies.11,14,16 Despite these studies, it remains unclear whether the LN location, number of metastatic LNs, LNR, or the number of retrieved LNs is more important. Current guidelines recommend radical resection in patients with T1b or T2 GBCA because of residual cancer or LN metastasis. However, even though there is a risk of LN metastasis, many clinical practices forgo the guidelines and perform limited resection. Recently, cholecystectomy and LN dissection without liver resection were investigated in patients with T2 GBCA,20 and the role of minimally invasive surgery was also explored.21,22 However, the minimum number of

retrieved LNs was not fully evaluated in this study, and thus, no consensus was reached on this topic. Significant differences in survival were observed between patients according to the cut-off values assigned for the number of positive LNs, LNR, and number of retrieved LNs. Logistic regression analysis revealed that LNR was a significant prognostic factor in patients at all stages of GBCA. However, the median TLNC in patients with an LNR of more than 0.5 was two, and among 14 patients, 11 patients had N2 disease. The 7th AJCC staging system classifies patients with N2 disease as stage IVB, and these patients have a poor prognosis.13 Interestingly, the LN location was not a significant prognostic factor in our study. It was a significant prognostic factor during

Figure 1. Overall survival according to total lymph node count (TLNC), positive lymph node count, and lymph node ratio (LNR) in patients with T3 gallbladder cancer. A. There is a significant survival difference (p ¼ 0.003) between patients in the TLNC <8 group and TLNC 8 group. B. There is a significant survival difference (p < 0.001) between the positive LN count <4 group and the positive LN count 4 group. C. There is a significant survival difference (p ¼ 0.001) between the LNR <0.5 group and the LNR 0.5 group.

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209

Table 3 Univariate and multivariate analysis for overall survival in patients with T3 disease. Variable

CA 19-9, U/mL Previous cholecystectomy LN dissection CBD resection Liver resection Extent of resection Adjuvant therapy Tumor differentiation Lymphovascular invasion Perineural invasion Node involvement No. retrieved LNs No. positive LNs LNR

Univariate analysis 37 Yes D2a Yes Yes R1 R2 Yes MD vs. WD PD vs. WD Yes Yes N1 vs. N0 N2 vs. N0 8 4 0.5

Multivariate analysis

HR

p

95% CI

2.5 0.135 0.61 0.891 0.718 2.573 7.578 1.99 1.665 3.65 2.777 1.581 1.659 3.291 0.35 4.942 4.721

0.028 0.05 0.187 0.757 0.427 0.025 <0.001 0.17 0.505 0.095 0.007 0.246 0.27 0.028 0.005 <0.001 <0.001

1.107e5.646 0.018e0.998 0.293e1.271 0.43e1.848 0.318e1.625 1.125e5.883 2.702e21.252 0.745e5.32 0.372e7.443 0.798e16.702 1.32e5.845 0.729e3.432 0.675e4.077 1.137e9.529 0.167e0.73 2.149e11.368 2.129e10.47

HR

p

95% CI

2.503

0.033

1.077e5.815

0.114 16.4

<0.001 <0.001

0.04e0.32 5.196e51.757

AJCC, American Joint Committee on Cancer; CA, carbohydrate antigen; CBD, common bile duct; CI, confidence interval; HR, hazard ratio; LN, lymph node; LNR, metastatic to retrieved lymph node ratio; MD, moderate differentiation; No, number; OS, overall survival; PD, poorly differentiated; WD, well-differentiated. a D2 dissection includes dissection of lymph nodes around the hepatoduodenal ligament, gastrohepatic ligament, celiac area, and para-aortic area (above and below the renal vein).

univariate analysis only. Among patients with N2 disease, two with less than four metastatic LNs had a prolonged OS duration (data not shown). Most patients with N2 disease exhibited advanced depth of tumor invasion and multiple LN metastases. Analysis of advanced-stage GBCA may reveal that LNR is a significant prognostic factor in patients of all stages. However, the Nagoya group reported that LNR was not a significant prognostic factor in patients with perihilar cholangiocarcinoma, and that low TLNC may contribute to misinterpretation of the LNR results.18 Previous studies showed that the minimum TLNC required to reach significance was six. Specifically, they reported that patients with no LN metastases and a TLNC of less than six had similarly poor survival rates compared to patients with positive LN metastases.16,23,24 However, in these studies, the median TLNC was less than six. In our study, the median TLNCs were 9.5, 13, and 21.5 in patients with T2, T3, and T4 GBCA, respectively, and LN metastases were found in 41.7% of patients with T2 GBCA. The rate of LN metastasis is similar to that of previous studies, but there was no difference in survival duration between patients with LN metastasis (median OS 96 months) and those without LN metastasis (median OS 96 months). Additionally, we found that only R2 resection is a significant prognostic factor in patients with T2 GBCA, which is consistent with a previous review (data not shown).25 Among patients with T2 GBCA, 51 (85%) had either no metastatic LNs (36 patients) or just one metastatic LN (15 patients). Several studies have reported that survival is better in patients with single LN metastases than in those with multiple LN metastases.11,18 Because of this finding, only the R0 resection was found to be a

significant prognostic factor, and LN parameters were not found to be prognostic in patients with T2 GBCA. Our study reveals that a minimum TLNC of eight was a significant prognostic factor in patients with T3 GBCA. Shirai et al. reported the extent of regional lymphadenectomy and its effect on long-term survival in GBCA.26 According to their report, pericholedochal (54%) and cystic duct (38%) lymphatic regions were the most prevalent sites of LN metastasis. However, retroportal (29%), posterior superior pancreaticoduodenal (25%), hepatic artery (25%), and right celiac (19%) node groups were other common metastasis sites. In this study, we found the median TLNC to be three in the pericholedochal and cystic duct node dissection group. If we include the retroportal node group, the median TLNC would have been six. With this information, it is important to consider that there may be residual LN metastases in the posterior superior pancreaticoduodenal, hepatic artery, and right celiac node groups, and that surgeons may not achieve complete R0 resection. Our study shows that, among patients with multiple LN metastases, only those who underwent extensive LN dissection had a higher 5-year survival. Of note, our results are based on surgical outcomes of five surgeons performing D2 dissections until 2006. Since that time, three surgeons have performed D2 dissections only when para-aortic LN metastasis was suspected during intraoperative inspection and palpation. This may have influenced the results of TLNC and number of metastatic LNs. However, even with a potential reduction in TLNC and number of metastatic LNs, the results still favored extensive LN dissection for improved survival.

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The ability to achieve complete R0 resection is an important prognostic factor in all cancer surgery, including surgery for GBCA, as GBCA is resistant to various chemotherapy and radiotherapy regimens. Our patients received several different adjuvant therapies. We found that the use of adjuvant therapies was a negative prognostic factor for OS in our study population. Most patients who received adjuvant therapy had a higher prevalence of PNI and/or more advanced T or N disease. However, previous reports on unresectable locally advanced biliary tract cancers have shown survival advantages with concurrent chemoradiotherapy.27,28 Our results regarding the influence of adjuvant therapy on survival may be limited, because not all patients eligible for adjuvant therapy underwent treatment due to personal preference or performance status. The role of adjuvant therapy after surgery should be further evaluated. Overall, our results suggest that achieving a minimal TLNC of eight may increase the likelihood of successful R0 resection and improve patient survival in advancedstage GBCA. There is currently no consensus regarding the adequate TLNC in GBCA. Although several studies have reported the minimum TLNC to be six, the median TLNC of these studies was less than six. Therefore, the actual minimum TLNC may be underestimated in these studies. Our study showed that a TLNC of eight was a significant prognostic factor in T3 GBCA. LN dissection achieving a TLNC of eight may increase the rate of R0 resection, prevent tumor migration, and allow for accurate staging. Additionally, a surgeon may elect to harvest more than eight nodes to ensure accurate information about staging and survival. Further studies are needed to determine whether these results can be applied to all stages of GBCA. Conflicts of interest The authors have no conflicts of interest to disclose.

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