Prognostic factors for pN2 non-small cell lung cancer: a comprehensive evidence from 73 studies involving 23,772 patients

Obojective Non-small-cell lung cancer (NSCLC) is a common malignancy. pN2 NSCLC, with pathologically confirmed ipsilateral mediastinal/subcarinal nodes metastasis, has been known as a very heterogeneous subgroup in terms of its anatomical, biological and patient characteristics. Prognostic factors based on patient characteristics were not well determined yet in this subgroup, and there is currently no standard treatment recommendation for these heterogeneous pN2 subjects. Apparent disagreements and inconsistency exist in study reports concerning the prognostic significance of certain factors in pN2 NSCLC, especially regarding to the issue about whether skip N2 metastasis benefit from surgery.Methods We therefore performed this comprehensive summary of the published literatures to draw a more precise and less uncertain conclusion. After a comprehensive literature search, a total of 73 studies involving 23,773 subjects were included according to eligibility criteria. Results As expected, most of the investigated factors, such as old age, male, advanced pathological T stage, advanced clinical N stage, multiple N2 stations, extended surgical resection (pneumonectomy), and incomplete resection, but not post-operation treatment (eg. chemotherapy and radiotherapy) were significantly associated with poor survival. However, skip N2 metastasis was favourable prognostic factors in operable pN2 NSCLC subjects. Other factors (histological type and primary tumour side) were neutral in terms of association with overall survival. We highlighted a number of important prognostic factors for pN2 NSCLC patients. Particularly, patients with skip N2 disease benefit from surgery. Conclusion Our findings could be used as reference information for decision-making in clinical practice and future study design.