Lymph node ratio (LNR) as a complementary staging system to TNM staging in salivary gland cancer

The role of lymph node ratio (LNR, ratio of metastatic to examined nodes) in the staging of multiple human malignancies has been reported. We aim to evaluate its value in salivary gland cancer (SGC).

Records of SGC patients from Surveillance, Epidemiology, and End Results database (SEER, training set, N = 4262) and Fudan University Shanghai Cancer Center (FUSCC, validating set, N = 154) were analyzed for the prognostic value of LNR. Kaplan-Meier survival estimates, the Log-rank χ² test and Cox proportional hazards model were used for univariate and multivariate analysis. Optimal LNR cutoff points were identified by X-tile.

Optimal LNR cutoff points classified patients into four risk groups, R0, R1 (≤ 0.17), R2 (0.17-0.56) and R3 (> 0.56), corresponding to 5-year cause-specific survival in SEER patients of 88.6%, 57.2%, 53.1% and 39.7%, disease-free survival in FUSCC patients of 69.2%, 63.3%, 34.6% and 0%, and disease-specific survival in FUSCC patients of 92.3%, 90.0%, 71.4% and 0%, respectively. Compared with TNM staging, TNM + R staging showed smaller AIC values and higher C-index values in the Cox regression model in both patient sets.

LNR classification should be considered as a complementary system to TNM staging and LNR classification based clinical trials deserve further research.