Predictors and Patterns of Lymph Node Metastasis in Small Peripheral Non-Small Cell Lung Cancer

Lobectomy is the standard treatment of early stage non-small cell lung cancer (NSCLC) and whether sublobar resection is appropriate for small peripheral small NSCLC or not is unclear. PET-CT is a powerful imaging modality for the detection of lymph node metastasis with a relatively low false-negative rate. We identified predictors and patterns to identify false-negative N(+) disease in PET-CT. A total of 435 consecutive cN0 peripheral NSCLC underwent curative-intent resections following PET-CT scans from January 2008 to December 2014 in our hospital, we analyzed patients’ clinicopathological data retrospectively. 171 patients with tumor size≤2cm were enrolled to identify predictors and patterns of lymph node metastases by multivariable analysis. The cut-off values, sensitivity and specificity for the predictors were calculated using a receiver operating characteristic curve. The patterns of lymph node metastases were also analyzed. In total, 9.4% (16/171) PET-CT-diagnosed N0 NSCLC cases were pathologically N1/N2 disease. The preoperative CEA was a unique independent risk factor for lymph node metastasis (OR = 0.914, 95 CI% = 0.85–0.98, P = 0.009). According to ROC curve, we divided the patients into two groups by CEA: the N(+) rates in the CEA ≤1.67 and CEA＞ 1.67 groups were 1.6% (1/64) and 14.0% (15/107), respectively (P =0.007). In 16 patients with lymph node metastasis, 7 were N1 disease, and 6 out of 9 N2 diseases were skip N2 disease. 93.5%(15/16) lymph node metastases were found in adenocarcinoma and 11 of them were single station metastases. The metastases rates in solid and subsolid lesions were 12.8%(16/125) and 0%(0/46)(P=0.007), retrospectively. Solid/mucinous/ micropapillary predominant adenocarcinoma were associated with LN metastases(31.2% vs 7.1%, P=0.01). The preoperative CEA was an independent risk factor for lymph node metastases in cN0 NSCLC with T ≤ 2cm. In patients with CEA＞1.67, sublobar resection should be avoided before thorough lymph node sampling that include intrapulmonary lymph node while patients with CEA ≤ 1.67 may be candidate for sublobar resection, especially in GGO lesions. In patients with solid/mucinous/ micropapillary predominant adenocarcinoma, sublobar resection should be avoided due to high LN metastases rate.