Define relative incomplete resection by highest mediastinal lymph node metastasis for non-small cell lung cancers: rationale based on prognosis analysis

Abstract

Purpose: Present research aimed to explore the rationale of defining RIR operations by metastatic status of highest nodes.

Patients and methods: 549 surgical patients, bearing pN2-NSCLCs, were enrolled in the current study. R1/R2 nodes on the right side and L4 nodes on the left were taken as the highest mediastinal lymph nodes. The operations were defined "Complete Resection (CR)" if the highest nodes were negative. Operations were otherwise "Relative Incomplete Resections (RIR)" if the nodes were positive. Exclusion criteria included: metastatic carcinomas or small cell lung cancer, prior history of induction therapy, exploratory thoracotomy, palliative resection, and massive pleural dissemination, as well as cases without "highest" mediastinal nodal pathology. The survival rate was calculated using the life-table and Kaplan-Meier method. Comparisons between groups were calculated using the Log-rank test.

Results: A total of 6865 lymph nodes (5705 mediastinal and 1160 regional, average 12.6±6.4 nodes for each patient) were removed. Total cases included 246 RIR (100 left and 146 right side) and 303 CR (108 left and 195 right). The overall 5-year survival rate was 22% and the median survival time was 28.29 months. Five-year survival rates of the CR and RIR group were statistically significant (29% and 13%, respectively p<0.0001). L4 and R1/R2 lymph nodes had similar position for defining RIR; no obvious survival difference was indicated between either side (p=0.464 in CR groups, p=0.647 in RIR groups). N2 subcategories and skip-metastasis were closely associated with highest nodal involvement (p<0.0001). Multivariate analysis showed CR/RIR assignment, tumor size, N2 disease stratification, pathological T status, and number of positive mediastinal nodes were risk factors for 5-year survival in the present case series.

Conclusion: Involvement of the highest mediastinal lymph nodes is highly predictive of poor prognosis and indicates an advanced stage of the disease. Therefore, it may be appropriate to assign R1/R2 or L4 as criterion for defining RIR or CR cases in surgical NSCLC cases.