Does Lymphadenectomy with at Least 15 Perigastric Lymph Nodes Retrieval Promise an Improved Survival for Gastric Cancer: A Retrospective Cohort Study in Southern China

Abstract

Background: Specific guidelines recommend at least 15 or 16 lymph nodes (LNs) be examined to adequately assess nodal category of gastric cancer (GC), but the requirement for minimum number of regional LNs retrieval is not mentioned. This study aims to investigate survival significance from various numbers of perigastric (N1) LNs retrieval and to determine an optimal number harvested in such region. Study design: From April 1994 to March 2012, 1003 resectable GC patients with at least 15 LNs examined were included. Patients with at least 15 N1 nodes retrieval were assigned into study group, with the rest into control group. The 5-year overall survival (OS) rate was compared between two groups, and an optimal number of examined N1 nodes was detected by a survival joinpoint analysis. Results: 635 (63.3%) patients in study group had median 22 (range, 15-75) N1 nodes and 3 (range, 0-74) positive N1 nodes retrieval, with median 10 (range, 0-14) N1 nodes and 1 (range, 0-29) metastatic N1 nodes examined in control group. The number of N1 nodes retrieval was associated with tumor location (P=0.007), tumor stage (P<0.001) and total number of harvested LNs ( r =0.691, P<0.001). Median survival time (79.0 vs. 72.0 months, P=0.462) and actual 5-year OS rate (41.0% vs. 39.2%, P=0.463) were slightly improved in study group compared with control group, with significance obtained via stage-by-stage analysis. The joinpoint analysis indicated that at least seven N1 nodes retrieval achieved survival significance (81.0 vs. 35.0 months, P=0.036), with survival superiority remained until reaching up to 15 N1 nodes. Conclusion: Adequate retrieval of perigastric LNs is essential for radical gastrectomy. A harvest of at least 7-15 perigastric LNs could achieve long-term survival benefit for GC patients.

Keywords: gastric cancer; lymphadenectomy; regional lymph nodes; survival; tumor staging.

Figure 1

The flow chart of this study. Abbreviations: GC, gastric cancer; LNs, lymph nodes; OS, overall survival; M1, synchronized tumor isolated outside of stomach; N1 stations, the first-tier lymph node stations (No. 1-6 stations).

Figure 2

The frequency distributions of lymph nodes retrieval. Cases with less than 15 LNs retrieved in total were excluded from this study. Right-skewed distribution is observed in either number of LNs retrieval (A) or positive LNs retrieval (B). N2 stations include No. 7-12 stations, with N2⁺ stations including No. 13 station and above stations. pN1 stage presents with 1~2 positive LNs retrieved in all stations, with pN2 for 3~7 positive LNs, pN3a for 8~16 positive LNs and pN3b for at least 17 positive LNs.

Figure 3

Linear correlations among levels of lymph nodes retrieval. (A) The number of LNs retrieved in total is correlated with the number of metastatic LNs across entire cohort (r=0.433, P=0.019). (B) The total number of LNs retrieval is strongly associated with the number of LNs retrieved in N1 stations (r=0.691, P<0.001). (C) The number of LNs retrieved in N1 stations is also correlated with the number of involved LNs in perigastric region (r=0.434, P=0.014).

Figure 4

Comparison of long-term overall survival rate between study group (N1≥15) and control group (N1<15) according to pathological stage. (A) stage IA; (B) stage IB; (C) stage IIA; (D) stage IIB; (E) stage IIIA; (F) stage IIIB; (G) stage IIIC; (H) all stages.

Figure 5

The joinpoint trend analysis for median survival at each count of perigastric LNs retrieval. The red dotted line below 0.05 at left Y-axis indicates survival significance in the current cohort; the black line indicates the median overall survival (right Y-axis), which slopes down at 7 and 15 X-axis, respectively.