Does N ratio affect survival in D1 and D2 lymph node dissection for gastric cancer?

Table 1 Case characteristics n (%)

	D1	D2	P value
Gender
M	61 (63.5)	71 (59.2)	0.512
F	35 (36.5)	49 (40.8)
Age (yr)
< 70	70 (72.9)	86 (71.7)	0.142
≥ 70	26 (27.1)	34 (28.3)
Surgical Procedure
TG	79 (82.3)	55 (45.8)	0.001
DSG	17 (17.7)	65 (54.2)
Anatomical localization of primary tumor
Proximal	9 (9.4)	9 (7.5)	0.087
Middle	39 (40.6)	43 (35.8)
Distal	33 (34.4)	59 (49.2)
Diffuse	15 (15.6)	9 (7.5)
Number of lymph nodes removed (mean ± SD)	14.4 ± 6.1	23.5 ± 9.3	0.022
Number of metastatic lymph nodes (mean ± SD)	3.8 ± 2.2	6.1 ± 4.6	0.034
T (Depth of invasion)
T1	8 (8.3)	9 (7.5)	0.056
T2	9 (9.4)	15 (12.5)
T3	59 (61.5)	75 (62.5)
T4	20 (20.8)	21 (17.5)
N (According to AJCC)
0	20 (20.8)	26 (21.7)	0.296
1	32 (33.3)	47 (39.2)
2	40 (41.7)	37 (30.8)
3	4 (4.2)	10 (8.3)
TNM stage
IA	2 (2.1)	6 (5.0)	0.001
IB	12 (12.5)	7 (5.8)
II	19 (19.8)	30 (25)
IIIA	42 (43.8)	58 (48.3)
IIIB	21 (21.9)	19 (15.8)
V	-	-
Pathology
Adenocarcinoma	77 (80.2)	97 80.8)	NA
Signet ring cell	4 (4.2)	18 (15.0)
MAC	10 (10.4)	2 (1.7)
Carcinoid tumor	2 (2.1)	-
Lymphoma	3 (3.1)	3 (2.5)
N ratio
0	12 (12.5)	19 (15.8)	0.001
1	29 (30.2)	34 (28.3)
2	39 (40.6.)	23 (19.2)
3	16 (16.7)	44 (36.7)
Lauren classification
Diffuse	47 (49.0)	52 (53.3)	0.424
Intestinal	49 (51.0)	68 (56.7)

D1: D1 lymphadenectomy; D2: D2 lymphadenectomy; M: Male; F: Female; N ratio: Node ratio; TG: Total gastrectomy; DSG: Distal subtotal gastrectomy; MAC: Mucinous adenocarcinoma; NA: Not available; AJCC: American Joint Committee on Cancer; TNM: Tumor nodule metastasis.

Table 2 Comparison of 5 year survivals in dissection 1 and dissection 2 dissection groups depending on N and N ratio n (%)

N	D	n	5 YS	P value	N ratio	n	5 YS	P value
N0	D1	20	6 (30.0%)	0.172	0	20	6 (30.0%)	0.389
	D2	26	13 (50.0%)			26	13 (50.0%)
N1	D1	32	4 (12.5%)	0.047	1	29	4 (13.8%)	0.070
	D2	47	15 (31.9%)			44	13 (29.5%)
N2	D1	40	6 (15.0%)	0.044	2	39	5 (12.8%)	0.192
	D2	37	1 (2.7%)			32	3 (9.4%)
N3	D1	4	NA	NA	3	16	1 (6.3%)	0.267
	D2	10	NA			44	0

D1: D1 lymphadenectomy; D2: D2 lymphadenectomy; N ratio: Node ratio; 5 YS: Five years survival; NA: Not available.

Table 3 Node ratios vs node classes n (%)

N ratio (metastatic/total number of lymph nodes removed)
	0(0)	1(0-9)	2(10-25)	3(> 25)	Total
D1 group
N0 (0)	20 (100)				20
N1 (1-6)	21 (65.6)	11 (34.4)			32
N2 (7-15)		28 (70.0)	12 (30.0)		40
N3 (> 15)				4 (100)	4
D2 group
N0 (0)	26 (100)				26
N1 (1-6)		37 (78.7)	6 (12.8)	4 (8.5)	47
N2 (7-15)			26 (70.3)	11 (29.7)	37
N3 (> 15)				10 (100)	10

D1: D1 lymphadenectomy; D2: D2 lymphadenectomy; N: Groups with respect to number of lymph nodes removed.