Prognostic impact based on tumor diameter of pathological N1 lymph node metastases for non-small cell lung cancer.

BACKGROUND

The N parameter in the tumor-node-metastasis (TNM) classification of lung cancer is categorized according to the location of nodal metastasis, while that for some other cancers are classified according to the size and number of metastatic foci. In lung cancer, the impact of size of nodal metastasis on prognosis is unclear. This analysis aims to examine whether it is possible to subdivide the pathological N (pN) factor based on the tumor diameter of lymph node metastases.

METHODS

We studied 35 cases of adenocarcinoma and 26 cases of squamous cell carcinoma of the lung. The maximum diameter of lymph node metastasis was measured, and the relationship between the maximum diameter of lymph node metastases and prognosis was investigated.

RESULTS

Squamous cell carcinoma cases had a significantly larger maximum tumor diameter of lymph node metastasis than adenocarcinoma cases (P=0.03). Based on receiver operating characteristic (ROC) curve results for the adenocarcinoma cases, we set 4 mm as a diameter cutoff value. The 5-year overall survival (OS) rate was 85.6% for patients with diameters ≤4 mm and 57.7% for those with diameters >4 mm; this difference was statistically significant (P=0.04). On univariate analysis using a Cox proportional hazards model, significant differences were observed in metastatic lymph node diameter (≤4 >4 mm) (P=0.04), sex (P=0.04), and pathological T (pT) status (pT1 and 2 pT3 and 4) (P=0.03). However, similar results were not obtained for patients with squamous cell carcinoma.

CONCLUSIONS

The tumor diameter of pathological N1 lymph node metastases impacts the prognosis of patients with lung adenocarcinoma. If pathological N1 can be further subdivided according to tumor diameter of lymph node metastases, a more accurate prognosis may become possible. However, pathological type must be considered for staging in lung cancer. While the pN parameter for most cancers considers tumor size of lymph node metastasis, this does not apply to lung cancer.