Abstract
OBJECTIVE: We used brain radiotherapy as a surrogate for the presence of brain metastases in patients with non-small cell lung cancer (NSCLC) to determine the prevalence of brain metastases using the Surveillance Epidemiology and End Results database. METHODS: Patients with NSCLC diagnosed between 1988 and 1997 were subdivided according to brain radiotherapy status at presentation into: "none" or "radiation therapy indicated." We calculated the frequency of brain radiotherapy use in all patients. Odds ratios (ORs) for the indication of brain radiotherapy were calculated for individual prespecified covariates of interest. All statistical tests were 2-sided and P<0.05 were considered significant. RESULTS: At presentation, brain radiotherapy was indicated in 10,963 (8.3%) of the 131,456 patients diagnosed with NSCLC between 1988 and 1997. On multivariable analysis the following were significantly associated with brain radiotherapy use: age (OR, 0.653 per 10 y increase in age; 95% confidence interval [CI]: 0.642, 0.665); female sex (OR, 1.05; 95% CI: 1.01, 1.10]); adenocarcinoma histology (HR, 1.67; 95% CI: 1.58, 1.76) or large cell or other histology (OR, 1.67; 95% CI: 1.57, 1.77); tumor size>3 cm (3.1 to 5 cm OR, 1.22; 95% CI: 1.14, 1.30 and >5 cm OR, 1.25; 95% CI: 1.17, 1.33); tumor grade >II (grade III OR, 1.82; 95% CI: 1.69, 1.95 and grade IV OR, 1.91; 95% CI: 1.73, 2.11); and nodal involvement N1 (OR, 1.33; 95% CI: 1.20, 1.47), N2 (OR, 2.24; 95% CI: 2.10, 2.40), and N3 (OR, 2.39; 95% CI: 2.19, 2.60). CONCLUSIONS: Brain radiotherapy is indicated in over 8% of patients with NSCLC at presentation. We demonstrated that the risk of brain metastasis at presentation may be stratified with the use of 6 clinical factors.