Swedish Lung Cancer Radiation Study Group: Predictive value of histology for radiotherapy response in patients with non-small cell lung cancer

The aim of the present study was to evaluate the potential predictive value of histology in non-small cell lung cancer (NSCLC) treated with curatively intended radiotherapy. In a collaborative effort among all the Swedish Oncology Departments, clinical data were collected for 1146 patients with a diagnosed non-small cell lung cancer subjected to curatively intended irradiation (⩾50 Gy) during the years 1990 to 2000. The included patients were identified based on a manual search of all medical and radiation charts at the oncology departments from which the individual patient data were collected. Only patients who did not have a histological diagnosis date and death date/last follow-up date were excluded (n = 141). Among the 1146 patients with non-small cell carcinoma eligible for analysis, 919 were diagnosed with either adenocarcinoma (n = 323) or squamous cell carcinoma (n = 596) and included in this study. The median survival for the 919 patients was 14.8 months, while the 5-year survival rate was 9.5%. Patients with adenocarcinoma had a significantly better overall survival compared with patients with squamous cell carcinoma (p = 0.0062, log-rank test). When comparing different stages, this survival benefit was most pronounced for stages IIA-IIB (p < 0.0001, log-rank test). The difference in survival between the two histological groups was statistically significant in a univariate Cox analysis (p = 0.0063) as well as in two multivariate Cox analyses including demographic and treatment variables (p = 0.037 and p = 0.048, respectively). In this large population based retrospective study we describe for the first time that patients with adenocarcinoma have a better survival after curatively intended radiation therapy in comparison with squamous cell carcinoma patients, particularly those with clinical stages IIA-IIB.