Novel perspective to evaluate the safety of segmentectomy: clinical significance of lobar and segmental lymph node metastasis in cT1N0M0 lung adenocarcinoma

Abstract

Objectives: The regularity of intrapulmonary lobar and segmental lymph node (LSN) metastasis in cT1N0M0 stage lung adenocarcinoma remains unclear. Thus, segmentectomy with uncertain LSN metastatic status remains a potential oncological risk. We aimed to facilitate more accurate determination of N staging and filter more suitable cases for segmentectomy.

Methods: A prospective study was performed from March 2014 to September 2016. A total of 196 patients diagnosed with cT1N0M0 stage lung adenocarcinoma were enrolled and received lobectomy together with mediastinal lymph node dissection. The intrapulmonary LSNs were dissected and classified as adjacent LSN or isolated LSN. The metastatic status of the LSNs together with the TNM staging were analysed. A comparison of the metastatic probability of isolated LSN was carried out considering the metastatic status of adjacent LSN, imaging features, smoking history, pathological subtypes, size of the lesions and serum level of tumour markers (carcinoembryonic antigen and Cyfra21-1).

Results: Among the 196 cases enrolled, 152 were confirmed as pN0, 36 as pN1, 6 as pN1 + N2 and 2 as skip pN2. When the LSNs had not been dissected, the false-negative rate for N staging was 9.0% (15 of 167). Patients with adjacent LSN metastasis (P < 0.001), solid nodule (P = 0.001), non-lepidic predominant invasive adenocarcinoma (P < 0.001), nodules with maximum diameter larger than 2 cm (P < 0.001) and those with elevated serum carcinoembryonic antigen level (>5 ng/ml) (P = 0.005) had a higher isolated LSN metastasis rate. No significant difference in isolated LSN metastasis rate was found between groups with or without smoking history (P = 0.90) and with different serum Cyfra21-1 levels (P = 0.14).

Conclusions: Dissection of intrapulmonary LSNs reduces the false-negative rate of lymph node metastasis. Solid nodule, non-lepidic predominant invasive adenocarcinoma, lung adenocarcinoma larger than 2 cm in maximum diameter or with elevated serum carcinoembryonic antigen level (>5 ng/ml) might not be suitable for segmentectomy. The lymph node sampling area during segmentectomy should include adjacent LSNs of the target segment. When metastasis to the adjacent LSNs is confirmed by fast-frozen pathology, segmentectomy would not be suitable.

Keywords: Lung adenocarcinoma; Lymph node; Segmentectomy; Tumour metastasis.