Background: To address social inequality in survival after lung cancer, it is important to consider how socioeconomic position (SEP) influences prognosis. We investigated whether SEP influenced receipt of first-line treatment and whether socioeconomic differences in survival could be explained by differences in stage, treatment and comorbidity.
Material and methods: In the Danish Lung Cancer Register, we identified 13 045 patients with lung cancer diagnosed in 2004-2010, with information on stage, histology, performance status and first-line treatment. We obtained age, gender, vital status, comorbid conditions and socioeconomic information (education, income and cohabitation status) from nationwide population-based registers. Associations between SEP and receipt of first-line treatment were analysed in multivariate logistic regression models and those with overall mortality in Cox regression models with stepwise inclusion of possible mediators.
Results: For both low- and high-stage lung cancer, adjusted ORs for first-line treatment were reduced in patients with short education and low income, although the OR for education did not reach statistical significance in men with high-stage disease. Patients with high-stage disease who lived alone were less likely to receive first-line treatment. The socioeconomic difference in overall survival was partly explained by differences in stage, treatment and comorbidity, although some differences remained after adjustment. Among patients with high-stage disease, the hazard ratio (HR) for death of those with low income was 1.12 (95% CI 1.05-1.19) in comparison with those with high income. Among patients with low-stage disease, those who lived alone had a 14% higher risk for dying (95% CI 1.05-1.25) than those who lived with a partner. The differences in risk for death by SEP were greatest in the first six months after diagnosis.
Conclusion: Socioeconomic differences in survival after lung cancer are partly explained by social inequality in stage, first-line treatment and comorbidity. Efforts should be made to improve early diagnosis and adherence to first-line treatment recommendations among disadvantaged lung cancer patients.