Is tumor diameter a risk factor for occult N1 metastasis in patients with peripheral non-small cell lung cancer which is smaller than 3 cm?

The optimum treatment option is surgery for clinical early stage non-small cell lung cancer. Despite all non-invasive and invasive staging effort, occult lymph-node metastasis can be detected in pathological staging. Here, we investigated whether there was any correlation between tumor diameter and occult lymph-node metastasis in N1 stations. Data of patient with non-small cell lung cancer clinical stage 1A were reviewed retrospectively. Those with tumor diameter smaller than 3 cm and pN0-pN1 in pathological staging were included in the study. Overall survival (OS) was calculated by Kaplan-Meier and survival differences between pN0 and pN1 groups were investigated by Log-Rank methods. Cut-off value of tumor diameter for lymph-node metastasis was investigated by Receiver-Operating Characteristics test. Significance between pN0-pN1 and other categorical groups was investigated with Pearson Chi-square or Fisher's exact tests. A total of 257 patients meet to criteria included in the study. Fifty-five (21.4%) of the patients were females. The mean age was 62.7 ± 8.5 and median tumor diameter was 20 mm (Range: 2-30 mm). We detected occult lymph-node metastasis at the N1 stations (pN1) in 33 patients (12.8%) in histopathological examination of resected specimens and lymph-node dissection materials. The cut-off value of tumor diameter was calculated as 21.5 mm for occult lymph-node metastasis by Receiver-Operating Characteristics analysis (Area Under Curved: 70.1%, p = 0.004). There was a significant correlation between pN1 positivity and high tumor diameter (p = 0.02). However, we did not find a correlation between the lymph-node metastasis and age, gender, tumor histopathology, tumor localization, and visceral pleural invasion. Tumor diameter may be an indicator for occult lymph-node metastasis in patients with clinical stage-1A non-small cell lung cancer. This result should be considered in patient with mass which larger than 21.5 mm and planned stereotactic body radiotherapy instead of surgery.