Subsequent thoracic cancers among patients diagnosed with lung cancer: a SEER database analysis

Background: Population-based data on the development of subsequent thoracic cancers following the initial diagnosis of lung cancer are scarce. We evaluated this clinical scenario in lung cancer patients registered within the Surveillance, Epidemiology and End Results (SEER) database.Methods: The SEER database (1988-2013) was queried using the SEER*Stat program to determine the clinico-pathological features of lung cancer patients who develop subsequent thoracic cancers as well as the characteristics of these subsequent cancers. Associations were ascertained with chi-squared tests and survival analysis was performed using Kaplan-Meier methods. Standardized incidence ratios (SIRs) were calculated to determine the risk of each type of subsequent cancer.Results: A total of 223,274 lung cancer patients were identified and included in the current study. In this cohort, 6387 patients developed subsequent thoracic cancers. The following were associated with a higher likelihood of second cancers: female gender, younger age, white race, adenocarcinoma histology, married, lower AJCC stage, earlier year of diagnosis and local treatment with surgery rather than radiotherapy (p<.0001 for all parameters). In the subset of patients with subsequent thoracic cancers, survival was best for patients with second primary breast cancer followed by patients with lung or esophageal cancer (p<.0001). SIR analyses showed an excess risk for the development of esophageal cancer and second primary lung cancer following an initial diagnosis of lung cancer. This risk persists regardless of gender or receipt of radiotherapy (p<.05 for all scenarios).Conclusion: There is an excess risk for the development of esophageal cancer and second primary lung cancer following an initial lung cancer diagnosis. This risk is present irrespective of gender or receipt of radiotherapy.