The prognostic impact of tumor size in resected stage I non-small cell lung cancer: evidence for a two thresholds tumor diameters classification.

Purpose: The current TNM staging system for non-small cell lung cancer subdivides stage IA and IB according to a tumor size threshold of 3 cm. Some authors have suggested that tumor size behaves as a continuous, but the optimal diameter thresholds to be adopted remain debated.

Methods: We conducted a retrospective study on 548 patients who underwent a complete surgical resection at our institute for stage IA and IB non-small cell lung cancer according to the current TNM staging system. Univariate and multiaviate analysis of overall and disease-specific survival were performed.

Results: Stage IA had an overall 5 years survival of 67% and a 5 years disease-specific survival of 85%. Stage IB had an overall 5 years of 49% and 5 years disease-specific survival of 53%. Tumors <2 cm had a significantly better survival than tumors > or =2 cm (overall survival: p=0.007; disease-specific survival: p=0.026), as well as tumors ranging from 2 to 5 cm in comparison with larger ones (overall survival: p=0.031; disease-specific survival: p=0.013). No significant difference was found between groups ranging from 2 to 5 cm. Tumors of 2-5 cm had 57% higher probability of death in comparison with tumors <2 cm and tumors >5 cm had a probability of death 60% higher than tumor of 2-5 cm. Age and tumor size (two thresholds diameter classification) resulted independent variables at multivariate analysis.

Conclusion: the definition of T factor in the staging system of non-small cell lung cancer should consider two cutoffs according to tumor size. Two and 5 cm represent appropriate thresholds diameters that define subgroups with significant different prognosis.