Long-term survivors of non-small cell lung cancer after radiation therapy: the significance of histological type.

To determine if histological type was a prognostic factor for non-small cell lung cancer (NSCLC), 67 two-year survivors were analyzed retrospectively after definitive radiation therapy (RT) for inoperable or unresectable Stage I-III NSCLC. There was no difference in short-term outcome (within 2 years) between patients with squamous cell carcinoma and patients with adenocarcinoma. After 2 years, the 5-year survival rate for the 2-year survivors was 56% for squamous cell carcinoma (n = 55) and 34% for adenocarcinoma (n = 12). According to degree of histologic differentiation, patients with poorly differentiated adenocarcinoma had a poorer outcome compared than those with well differentiated adenocarcinoma and squamous cell carcinoma as a whole. Among progression-free patients at the end of 2 years, 97% of patients with squamous cell carcinoma survived without evidence of disease for more than 5 years. Disease-free 2-year survival should be substituted for 5-year survival in patients with squamous cell carcinoma treated with RT.