Metastatic lymph node burden impacts overall survival in submandibular gland cancer

Abstract

Objective: To assess the effect of the number of positive lymph nodes (LNs) on the overall survival (OS) of patients with submandibular gland cancer (SmGC).

Methods: Patients who had undergone neck dissection for SmGC were retrospectively enrolled in this study. The effect of the American Joint Committee on Cancer (AJCC) N stage, the number of positive LNs, LN size, LN ratio, and extranodal extension (ENE) on OS and recurrence-free survival (RFS) was evaluated using Cox analysis. Prognostic models were proposed based on the identified significant variable, and their performance was compared using hazard consistency and discrimination.

Results: In total, 129 patients were included in this study. The number of positive LNs rather than LN ratio, LN size, and ENE was associated with OS. A prognostic model based on the number of positive LNs (0 vs. 1-2 vs. 3+) demonstrated a higher likelihood ratio and Harrell's C index than those according to the 7th/8th edition of the AJCC N stage in predicting OS and RFS.

Conclusions: The effect of LN metastasis on OS and RFS was mainly determined by the number of positive LNs. A validation of this finding is warranted in adenoid cystic carcinomas that were not included in this study.

Keywords: AJCC stage; lymph node metastasis; number of positive lymph nodes; overall survival; submandibular gland cancer.

Figure 1

Overall survival plots of different lymph node (LN) status. (A) Survival plot for the 8th AJCC N stage: a significant difference existed among the N0, N1, N2, and N3 groups (Log-rank test, p<0.001); (B) Survival plot for the 7th AJCC N stage: a significant difference existed among the N0, N1, N2, and N3 groups (Log-rank test, p<0.001); (C) Survival plot for the LN metastasis burden: significant difference existed among groups with different metastatic burden (Log-rank test, p<0.001); and (D) Survival plot for different number of metastatic LNs: significant difference existed among the different subgroups (Log-rank test, p<0.001).

Figure 2

Recurrence-free survival plots of different lymph node (LN) status. (A) Survival plot for the 8th AJCC N stage: significant difference existed among the N0, N1, N2, and N3 groups (Log-rank test, p<0.001); (B) Survival plot for the 7th AJCC N stage: significant difference existed among the N0, N1, N2, and N3 groups (Log-rank test, p<0.001); (C) Survival plot for the LN metastasis burden: significant difference existed among groups with different metastatic burden (Log-rank test, p<0.001); and (D) Survival plot for different number of metastatic LNs: significant difference existed among the different subgroups (Log-rank test, p<0.001).