Incidence, Risk Factors, and Analysis of Survival of Unexpected N2 Disease in Stage I Non-Small Cell Lung Cancer.

Background To evaluate the incidence, predictors, and survival of unexpected pN2 disease in patients with clinical stage I non-small cell lung cancer. Methods This is a retrospective observational multicenter study on all consecutive patients operated for clinical stage I non-small cell lung cancer from January 2006 to December 2012. Medical records were reviewed to investigate the incidence and risk factors for unexpected pN2 disease. Then, the survival of patients with unexpected pN2 disease was statistically compared with that of patients with clinical N2 disease operated after induction therapy in the same period. Results Our study population counted 901 patients. An incidence of 12% (108/901) unexpected pN2 disease was found. Among 3,389 lymph nodes sampled, 124 distinct metastases were found. Of the 108 patients, 92 (85%) had metastases in single N2 station and 16 (15%) patients had disease in multiple N2 stations; 47 (44%) had pN2 disease without pN1 involvement (skip metastases) and 61/108 (56%) had also pN1 metastases. Factors associated with unexpected pN2 disease were central tumor location (p < 0.003), cT2a (p < 0.0001) and pT2a stage (p < 0.0001), pN1 disease (p = 0.004), and a standard uptake value > 4.0 (0.007). Patients with pN2 disease compared with patients with cN2 disease presented a better median overall survival (56 versus 20 months; p = 0.001) and disease-free survival (46 versus 11 months; p < 0.0001). Conclusions The preoperative effort to discover unexpected pN2 disease in patients with clinical stage I non-small cell lung cancer is not justified, considering their good survival. Thus, preoperative invasive mediastinal procedures in such cases are not indicated.