Does anatomical location-based metastatic lymph node density affect prognosis in lung cancer patients?

The newly proposed N subclassification (new-N) was compared with the combined anatomical location and ratio of the number of metastatic lymph nodes to the total number of resected lymph nodes (anatomic-LNR) in terms of prognosis in resected lung cancer patients.

Between 2005 and 2018, 961 patients who underwent lung cancer resection were catergorized into the pN1-single (N1a; n = 281), pN1-multiple (N1b; n = 182), pN2-single with skip metastasis (N2a1; n = 116), pN2-single with N1 metastasis (N2a2; n = 222) and pN2-multiple (N2b; n = 160) groups based on new-N. The optimal cut-off points for survival in pN1 and pN2 patients were determined using the best sensitivity and specificity scores, calculated using receiver operating characteristic analysis.

The difference in survival between N1a and N1b patients was statistically significant (P = 0.001), but there was no significant difference in the survival rates of N1b and N2a1 (P = 0.52). The survival curves for N2a1 and N2a2 patients almost overlapped (P = 0.143). N2a2 patients showed a better survival rate than N2b patients, with no significant difference (P = 0.132). The cut-off points for LNR were 0.10 and 0.25 for pN1 and pN2 patients, respectively, according to receiver operating characteristic analysis for survival. Based on receiver operating characteristic analysis, pN patients were categorized into the N1-lowLNR (n = 232), N1-highLNR (n = 231), N2-lowLNR (n = 266) and N2-highLNR (n = 232) groups. The 5-year survival rate was 62.9%, 49.8%, 41.1% and 27.1% for N1-lowLNR, N1-highLNR, N2-lowLNR and N2-highLNR, respectively (P < 0.001).

LowLNR is associated with better survival than highLNR in resected lung cancer patients. Anatomic-LNR shows a high discriminatory power for prognosis.