Disparities in cancer incidence, stage at diagnosis, treatment and mortality across socioeconomic groups in Finland: a register-based population study.

Background: Socioeconomic inequalities in various cancer-related indicators exist globally, but the evidence is fragmented even within countries. We aim to assess disparities in cancer incidence, stage at diagnosis, treatment and mortality by socioeconomic status (SES, measured as education and income) in Finland across the entire cancer journey. Methods: Among the total Finnish population aged 30+ years, we identified those newly diagnosed with cancer between 2000-2019 based on Finnish Population Register and Cancer Register data. We calculated standardised rate ratios (SRRs) to compare incidence between SES groups. We used logistic regression models to estimate OR of being diagnosed with later stage cancer and of receiving specific treatments, and Cox models to estimate HR of mortality across SES groups. Findings: Among 4 536 724 Finnish residents, 240 746 men and 228 776 women were newly diagnosed with cancer between 2000 and 2019. Systematic disparities were observed for incidence, stage at diagnosis, treatment and mortality for all cancers and for most types of cancers. Among both men (SRR 1.17, 95% CI 1.16 to 1.19) and women (SRR 1.05, 95% CI 1.04 to 1.06), those with lower education had higher total cancer incidence rates than those with higher education. Patients with lower education had higher odds of being diagnosed with stage IV cancer than patients with higher education (men: OR 1.10, 95% CI 1.08 to 1.12; women: OR 1.15, 95% CI 1.13 to 1.17). Both male and female patients with lower education had a lower likelihood of being treated with surgery, chemotherapy and radiation than patients with higher education. Finally, patients with lower education had higher mortality rates than patients with higher education (men: HR 1.13, 95% CI 1.10 to 1.16; women: HR 1.14, 95% CI 1.11 to 1.17). Similar patterns were observed by income. Conclusions: Low SES individuals were disadvantaged in all aspects of their cancer journey for total cancer and most cancer types.