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STOMACH
Οriginal Paper
Impact of Body Mass Index on Number of Lymph Nodes Retrieved in Gastric Cancer Patients Wafi Attaallah, Kivilcim Uprak, Mirhalik Javadov and Cumhur Yegen Marmara University School of Medicine, Department of General Surgery, Istanbul, Turkey
Corresponding author: Wafi Attaallah, MD, Marmara University Pendik Teaching and Research Hospital, Department of General Surgery, Fevzi Cakmak mah. Mimar Sinan cad. 41, Ustkaynarca, Pendik, Istanbul, 34899 Turkey; Tel.: +90 216 657 06 06; Fax: +90 216 657 06 95; E-mail:
[email protected]
ABSTRACT
Background/Aims: The aim of this study was to assess the influence of obesity on the number of the dissected lymph nodes in patients who underwent gastrectomy for gastric adenocarcinoma. Methodology: Thirty eight Patients with gastric adenocarcinoma who underwent curative gastrectomy at one center between April 2012 and December 2012 were eligible for the study. According to their body mass index (BMI) values before surgery patients with BMI >24.9 kg/m2 were defined as obese. Patients with BMI ≤24.9 kg/ m2 were defined as normal group. The number of retrieved lymph nodes and metastatic lymph nodes were obtained from pathology re ports. Results:
Among 38 patients there were 17 (45%) patients had BMI ≤ 24.9kg/m2 (normal group),while 21(%55) patients had BMI > 24.9 kg/m2 (obese group). The median number of retrieved lymph nodes in obese patients who underwent total gastrectomy was significantly higher compared to the normal patients underwent the same procedure. Conclusion: In this study we showed that the obesity affects the outcomes of surgery in gastric cancer. Furthermore, the total number of retrieved lymph nodes in obese patients who underwent total gastrectomy was higher than that in non-obese patients.
INTRODUCTION Some studies have shown poorer surgical outcomes in the surgical treatment of gastric cancer in obese patients (1-4) whereas others did not show significant difference in surgical outcomes between obese and nonobese patients (5,6). The body mass index (BMI) has often been used to describe the extent of obesity because it can easily be calculated from one’s height and weight. Surgeons may expect difficulties in performing gastrectomy on patients with high BMI, but it is not always the case. In some cancer studies it has been shown that the number of the dissected lymph nodes was higher in obese patients (7). Research on the impact of body mass index on the number of lymph node retrieved in patients with gastric cancer remains limited and results are controversial. The aim of this study was to assess the influence of obesity on the number of the dissected lymph nodes in patients who underwent gastrectomy for gastric adenocarcinoma.
tients were eligible for inclusion in this study. Patients were classified into two groups by BMI. Patients were prouped according to the WHO’s definition of obesity for the Asia-Pacific region. According to their body mass index (BMI) values before surgery patients with BMI >24.9 kg/m2 were defined as obese. Patients with BMI ≤24.9 kg/ m2 were defined as normal group.
METHODOLOGY Patients with gastric adenocarcinoma who underwent curative gastrectomy at our institution between April 2012 and December 2012 were investigated for the study. Eligible patients were identified through retrospective reviews of patient case records. The inclusion criteria were: 1) history of open total or subtotal gastrectomy; 2) D1 lymphadenectomy; and 3) patients who have BMI records before operation. Exclusion criteria were: 1) stage 4 disease; 2) retrieved lymph nodes less than 15; and 3) no records of BMI before surgery. Among a total of 53 patients who were operated 38 paHepato-Gastroenterology 2014; 61:2425-2427 doi 10.5754/hge14672 © H.G.E. Update Medical Publishing S.A., Athens-Stuttgart
Clinical data Information on age, gender, location of gastric cancer, histological diagnosis, radiological investigations, surgical procedure, pathological TNM stage and the (neo) adjuvant treatment were obtained from the medical records. All patients were staged preoperatively by us ing computerized tomography (CT) scans only. In some patients, magnetic resonance imaging or positron emission tomography-CT scan were obtained during the preoperative evaluation, if needed. After surgery, tumors were assessed for histological type, grade, stage, vascular invasion, lymphatic invasion and perineural invasion. The number of examined lymph nodes, the number of determined metastatic lymph nodes were determined for each patient. All patients underwent a standard total or subtotal gastrectomy and a regional lymphadenectomy (D1 dissection) with tumor-free surgical and circumferential margins. Lymph nodes in the specimen were recovered by in vitro mesenteric dissection. Data on lymph node status were obtained from pathology reports. Tumors were staged according to the current American Joint Commission on Cancer (AJCC 2010) TNM staging system.
Key Words:
Gastric cancer; Lymph node; Body Mass Index; Obesity.
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Hepato-Gastroenterology 61 (2014)
Attaallah W, Uprak K, Javadov M, Yegen C
TABLE 1. Demographics and surgical characterisitcs of patients (n = 38). N=38 (%100)
Age
Gender
Male Female BMI (kg/m2) Surgical procedure: Total gastrectomy Subtotal gastrctomy
25 (%66) 13 (%34)
Number of retrieved lymph nodes
21 (%55) 17 (%45)
Number of metastatic lymph nodes
Median (Min-Max)
61 (31-80)
26 (20-43) 20 (15-57) 5(0-42)
TABLE 2. Comparing outcomes of patients with high (BMI >24.9 kg/m2) and low (BMI ≤ 24.9 kg/m2) BMI.
Age [Median (Min-Max)] Gender Male Female BMI kg/m2
Obese group (BMI >24.9) n= 21
Normal group (BMI ≤ 24.9) n=17
P value
59 (43-80)
61 (31-69)
0.6
31±5
23±2
0.004
0.018
12 (%57) 9 (43%)
13 (%76) 4 (%24)
Number of retrieved lymph nodes
18 (15-51)
21 (15-57)
Number of metastatic lymph nodes
8 (%38) 13 (%62) 3 (0-42)
13 (%76) 4 (%24)
Surgical procedure: Total gastrectomy Subtotal gastrectomy
6 (0-21)
0.21
0.70
0.25
TABLE 3. Comparing outcomes of patients with high (BMI >24.9 kg/m2) and low (BMI ≤ 24.9 kg/m2) BMI in patients with total gastrectomy. Obese Normal group group (BMI ≤ 24.9) P value (BMI >24.9) n=13 n= 8 Age [Median (Min-Max)] 72 (50-80) 60 (31-69) 1.0 Gender Male Female
Number of retrieved lymph nodes Number of metastatic lymph nodes
5 (%63) 3 (37%)
30 (20-51) 7 (0-42)
11 (%85) 2 (%15)
21 (15-57) 6 (0-21)
0.33
0.027 0.83
Statistical analysis Background clinical data were analyzed using the ttest and Mann-Whitney U test for continuous data and Fisher’s exact test or the Chi squared test for categorical data. Data were analyzed using SPSS for Windows, version 17. All tests were two-sided and p-values below 0.05 were considered statistically significant. RESULTS 38 patients were included in this study. Twenty-five (66%) were male and thirteen (34%) were female. The median age was 61 (31-80) years. The median body mass index was 26 (20-43) kg/m2. Total gastrectomy was performed on 21 (55%) patients and subtotal gastrectomy was performed on 17 patients (45%). The me-
dian number of retrieved lymph nodes was 20 (15-57) (Table 1). Patients were grouped according to their body mass index (BMI) values before surgery. The normal group [n=17 (45%)] included the patients with BMI ≤ 24.9kg/ m2, and the obese group [n=21 (%55)] included the patients with BMI > 24.9 kg/m2. The mean BMI in the obese group was 31±5 kg/m2 while it was 23±2 kg/m2 in the normal group. The difference between the two means was statistically significant (p=0.004). No statistical difference (p=0.70) in the median number of the retrieved lymph nodes was found between the obese group (18 nodes, range: 15-51) and the normal group (21 nodes, range: 15-57). Additionally, there was no significant difference between the two groups in terms of number of metastatic lymph nodes (p=0.25). Total gastrectomy was performed more frequently in the normal group (76%) compared to the obese group (38%) (p=0.018) (Table 2). There was no significant difference between males and females in terms of the number of retrieved and metastatic lymph nodes (p=0.75 and p=0.25 respectively). Interestingly, we found that the median number of retrieved lymph nodes in obese patients who underwent total gastrectomy (n=8) was significantly higher compared to the normal patients (n=13) underwent the same procedure [30 nodes (range: 20-51) and 21 nodes (range: 15-57) respectively; p=0.027)]. No significant difference was found between the two groups of patients who underwent total gastrectomy in terms of age, gender and number of metastatic lymph nodes (p=1.0, p=0.33 and p=0.7 respectively) (Table 3). In contrast, the median number of retrieved lymph nodes was not significantly different between the obese (n=13) and non-obese patients (n=4) who underwent subtotal gastrectomy (p=0.7). DISCUSSION Thirty-eight patients with gastric adenocarcinoma who underwent gastrectomy in one center were included in this study. According to their body mass index, patients were classified as normal (≤24.9 kg/m2) or obese (>24.9 kg/m2). In this study, we found that the total number of lymph nodes retrieved in total gastrectomy was significantly higher in obese patients compared to non-obese patients. Research on the relationship between BMI and the number of retrieved lymph nodes during gastric cancer surgery remains limited and controversial results were obtained. Major limitations of this study are the small sample size, the differences in treatment procedures and the retrospective design of the study. It was reported that at least 15 lymph nodes have to be retrieved in gastric cancer surgery to make accurate TNM staging (8). For this reason we excluded patients from whom less than 15 lymph nodes were retrieved. To predict the impact of obesity on surgical outcomes, it is necessary to quantify the extent of obesity, which could be measured by performing computerized tomography (CT) scanning of the whole body, and calculating the actual area of body fat. However, this method is difficult and time consuming. BMI is more suitable alternative. BMI can be easily calculated from height and weight, is used to describe the extent of obesity and to predict the outcome of surgery (9-11). It must be emphasized
Number of Lymph Nodes Retrieved in Gastric Cancer
Hepato-Gastroenterology 61 (2014)
that BMI is represented by a number, irrespective of ethnic group and gender. Regarding ethnic groups, a number of studies have shown discordance between BMI and the actual proportion of body fat (12,13). Compared with Caucasians, Asians have higher percentage of body fat at a given BMI. Different cut-off values are being applied for different ethnic groups, and many Asian countries adopt a lower cut-off value for obesity at BMI ≥ 25kg/m2 while many Western countries adopt a higher cut-off value at BMI ≥30 kg/m2 (14). While differences in percentage body fat by ethnic groups have been shown, it has also been suggested that differences in body fat distribution between men and women do exist. Women tend to accumulate less adipose tissue in the visceral area, and have a lower ratio of abdominal visceral to mid-thigh adipose tissue than men (15-18). Some studies have investigated the impact of visceral fat volume on surgical outcomes and poorer surgical outcomes were seen in patients with larger volume of visceral fat (19). Since differences in visceral fat volume do exist by gender, we analysed the impact of gender on the retrieved lymph node number. We showed that the number of retrieved lymph node in gastric cancer is not affected by gender. Seung Soo Lee et al. have reported that difference in surgical outcomes including lymph nodes number may exist by genders. But in his study he showed that the number of resected lymph nodes were not significantly different between the male and the female groups (20). Instead of conducting abdominal CT scans analysis, we added gender to BMI and evaluated its impact on surgical outcomes. When predicting surgical outcomes of obese patients, consideration of gender, as well as BMI, may minimize the discordance between obesity and surgical outcomes. In the operating room, more experienced hands of surgeons and assistants may be required while performing
surgery on obese male patients. When interpreting or comparing surgical outcomes following abdominal surgery, patient gender, as well as BMI, must be considered. Kvist et al. have shown that, in females, visceral adipose tissue does not increase until the accumulation of total adipose tissue has reached a certain extent, and above which the ratio of visceral adipose tissue and total adipose tissue is similar between male and female (16). The number of lymph nodes resected by BMI remains controversial. Some studies have reported decreased number of resected lymph nodes in patients with high BMI (1), whereas others reported no such difference (5,6). Although all patients underwent a certain level of lymph node dissection in these studies, some differences of the extent of lymph node dissection within that certain level may still be allowed between obese and nonobese patients. It was reported that this accounts for the differences in the number of resected lymph nodes in some studies. However, the association between BMI and the number of retrieved lymph nodes is not clear in gastric cancer. In this study although standardized operations were performed on patients regardless of the extent of obesity, the number of resected lymph nodes was higher in obese patients. It was reported that the number of the dissected lymph nodes was higher in obese patients but there was no correlation between metastatic lymph node number and BMI in breast cancer (7). However, based on these retrospective results, more comprehensively planned, prospective, randomized controlled studies need to be conducted. In conclusion, in this study we showed that the obesity affects the outcomes of surgery in gastric cancer. Furthermore, the total number of retrieved lymph nodes in obese patients who underwent total gastrectomy for gastric adenocarcinoma was higher than that in nonobese patients.
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