The prognostic value of N-ratio in patients with gastric cancer: validation in a large, multicenter series.
OBJECTIVE
The proportion between metastatic and examined lymph nodes (N-ratio) has been proposed as an independent prognostic factor in patients with gastric cancer. In the present work we validated the reliability of N-ratio in a large, multicenter series.


METHODS
We retrospectively reviewed the data of 1853 patients who underwent radical resection for gastric carcinoma. Survival of patients with >15 (Group-1, n=1421) and those with < or =15 (Group-2, n=432) lymph nodes examined was separately analyzed in order to evaluate the influence of lymph node dissection on disease staging. N-ratio categories (N-ratio 0, 0%; N-ratio 1, 1-9%; N-ratio 2, 10-25%; N-ratio 3, >25%) were determined by the best cut-off approach.


RESULTS
At multivariate analysis, N-ratio (but not TNM N-category) was retained as an independent prognostic factor both in Group-1 and Group-2 (HR for N-ratio 1, N-ratio 2 and N-ratio 3=1.67, 2.96 and 6.59, and 1.56, 2.68 and 4.28, respectively). After a median follow-up of 45.5 months, the 5-year overall survival rates of TNM N0, N1 and N2 patients were significantly different in Group-1 vs Group-2. This was not the case when adopting the N-ratio classification, suggesting that a low number of excised lymph nodes can lead to patients being understaged using the N-category, but not N-ratio. Moreover, N-ratio identified subsets of patients with significantly different survival rates within TNM N1 and N2 categories in both groups.


CONCLUSIONS
N-ratio is a simple and reproducible prognostic tool that can stratify patients with gastric cancer, including those cases with limited lymph node dissection. These data support the rationale to propose the implementation of N-ratio into the current TNM staging system.
Marchet
A
A
Clinica Chirurgica II, University of Padova, Padova, Italy.
Mocellin
S
S
Ambrosi
A
A
de Manzoni
G
G
Di Leo
A
A
Marrelli
D
D
Roviello
F
F
Morgagni
P
P
Saragoni
L
L
Natalini
G
G
De Santis
F
F
Baiocchi
L
L
Coniglio
A
A
Nitti
D
D
D000230:Adenocarcinoma / Q000401:mortality / Q000556:secondary* / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D005260:Female; D005743:Gastrectomy / Q000379:methods; D006801:Humans; D007150:Immunohistochemistry; D008197:Lymph Node Excision / Q000706:statistics & numerical data; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D015999:Multivariate Analysis; D009367:Neoplasm Staging / Q000379:methods*; D011237:Predictive Value of Tests; D011336:Probability; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D013274:Stomach Neoplasms / Q000401:mortality / Q000473:pathology* / Q000601:surgery*; D016019:Survival Analysis