Effect of a prior thyroid cancer on the survival of lung cancer patients: a retrospective study based on SEER database

Purpose The effect of a history of thyroid cancer on the prognosis of lung cancer patients has not been fully investigated. Therefore, we aimed to evaluate this effect based on a large cohort. Methods Data of 154844 lung cancer patients, of whom 406 had prior thyroid cancer, were collected from SEER database. Primary survival analysis was conducted between patients with and without prior thyroid cancer using Kaplan–Meier method. Secondary survival analysis was conducted to investigate the effects of the stage and histological subtype of the prior thyroid cancer on the survival of lung cancer patients. Propensity adjustment was used to reduce confounding effect. Results Compared to patients without prior malignancy, patients with prior thyroid cancer were predominantly female (72.4% vs. 48.7%, p < 0.001), had lower stage (proportion of localized tumor: 40.4% vs. 25.6%, p < 0.001), and larger proportion of surgery (52.2% vs. 29.4%, p < 0.001), and had better survival (5-year survival rate: 55.53% vs. 33.16%, p < 0.001). After propensity adjustment, the survival was similar between the groups (5-year survival rate: 55.53% vs. 51.78%, p = 0.24). The survival of patients with different stages (localized tumor vs. regional tumor: p = 0.88) or different histological subtypes ( p = 0.46) of prior thyroid cancer were comparable. Conclusion Survival of lung cancer patients with or without prior thyroid cancer was similar after propensity adjustment, and the stage or histological subtype of the prior thyroid cancer had no significant effect on the survival of lung cancer patients.