Socioeconomic status is not associated with survival in patients with brain metastases treated with stereotactic radiotherapy

Background and purpose In most cancer sites a low socioeconomic status (SES) is consistently associated with poorer survival. For brain metastasis, this relation is not well understood. Therefore, we studied the effect of SES on survival in Dutch brain metastasis patients treated with stereotactic radiosurgery in a tertiary radiotherapy facility. Materials and methods We retrospectively studied 404 consecutive patients treated with stereotactic radiosurgery for brain metastases in a tertiary referral centre between 2012 and 2017. Baseline prognostic factors for survival were collected. The SES score was based on education, income and employment. Cox proportional hazard models were made, corrected for the relevant variables identified from a directed acyclic graph (DAG). Adjustments were made in two ways in order to obtain comprehensive results: correcting for confounders (total effect), and correcting for confounders and mediating factors (direct effect). Results Unadjusted, estimation of the linear effect of SES on survival resulted in a HR of 0.92 (95%CI 0.82 – 1.04). The total effect of SES was achieved by correcting for age, resulting in a HR of 0.95, with a 95% CI of 0.84 – 1.07. The direct effect gave a HR of 0.96 (95%CI 0.84 – 1.10). Conclusion SES was not associated with survival in patients with brain metastases undergoing radiation therapy. When correcting for clinical variables, we found no significant relationship between SES and survival, with HRs suggesting limited clinical impact. The results suggest that patients’ survival outcomes after contemporary cancer treatment are unrelated to their employment status, education status and annual income.