Background: In patients with non-small cell lung cancer (NSCLC) and normal mediastinum, the central tumor location predicts occult nodal disease (both N1 and N2). We evaluated a novel definition of central location based on a geometrical measurement of the tumor location within the lung that could predict N2, N1, or both.
Methods: This retrospective study included patients with confirmed NSCLC, radiologically and metabolically staged T1 N0 M0, who underwent invasive mediastinal staging and/or lung resection. The central tumor location was measured considering 2 ratios. The inner margin ratio (IMR) and outer margin ratio (OMR) were both calculated as the distance from the inner margin of the lung to both margins of the tumor (inner [IMR], outer [OMR]) divided by the lung width. Optimal cutoffs for IMR and OMR were calculated. Tumors with values lower than the cutoffs were considered central. Prevalences of N1 and N2 upstaging were estimated and bivariate logistic regression analysis was performed to predict the odds of N1 and N2 upstaging using IMR and OMR cutoffs.
Results: A total of 209 patients were included. The prevalence of N1 and N2 upstaging was 11% and 5.3%, respectively. Cutoffs of 0.5 for IMR and 0.64 for OMR were estimated. Both ratios predicted N1 upstaging (adjusted odds ratio [95% confidence interval]: 4.2 [1.5-12]; P < .007; area under the curve, 0.65) but did not predict N2 upstaging.
Conclusions: Central tumor location can be assessed by means of IMR and OMR and predicts N1 upstaging in patients with radiologically and metabolically T1 N0 M0 tumors. This is important for the selection of patients for therapies that require N0 tumors.
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