Socioeconomic Inequalities in Colorectal Cancer Survival in Southern Spain: A Multilevel Population-Based Cohort Study

Abstract

Background

Colorectal cancer (CRC) is the most frequently diagnosed cancer in Spain. Socioeconomic inequalities in cancer survival are not documented in Spain. We aim to study the association of socioeconomic inequalities with overall mortality and survival among CRC patients in southern Spain.

Methods

We conducted a multilevel population-based cohort study, including CRC cases for the period 2011–2013. The study time-to-event outcome was death, and the primary exposure was CRC patients’ socioeconomic status assessed by the Spanish deprivation index at the census tract level. We used a mixed-effects flexible hazard model, including census tract as a random intercept, to derive overall survival estimates by deprivation.

Results

Among 3589 CRC patients and 12,148 person-years at risk (pyr), 964 patients died before the end of the follow-up. Mortality by deprivation showed the highest mortality rate for the most deprived group (96.2 per 1000 pyr, 95% CI: 84.0–110.2). After adjusting for sex, age, cancer stage, and the area of residence, the most deprived had a 60% higher excess mortality risk than the less deprived group (excess mortality risk ratio: 1.6, 95% CI: 1.1–2.3).

Conclusions

We found a consistent association between deprivation and CRC excess mortality and survival. The reasons behind these inequalities need further investigation in order to improve equality cancer outcomes in all social groups.

Keywords:

• socioeconomic inequalities
• colorectal cancer
• survival
• population-based epidemiology
• epidemiological methods
• multilevel

Data Sharing Statement

The data are held by the Regional Government of Andalusia and the Andalusian Health Department. The code used in analyses is provided as a supplementary file.

Author Contributions

MALF designed the study, developed the analysis, and wrote the article. All authors contributed to data analysis, drafting or revising the article, gave final approval of the version to be published, and agree to be accountable for all aspects of the work.

Disclosure

The authors have declared that no competing interests exist.

Additional information

Funding

M.A.L.F. received support from the Instituto de Salud Carlos III, Madrid, Spain (grant/award no. CP17/00206-EU-FEDER). This work was supported by the Instituto de Salud Carlos III, Madrid, Spain [EU-FEDER-FIS PI-18/01593], the Consortium for Biomedical Research in Epidemiology and Public Health (CIBER en Epidemiología y Salud Pública), the Cancer Epidemiological Surveillance Subprogram (VICA) from the Instituto de Salud Carlos III, Madrid, Spain, and the Andalusian Department of Health [PI-0152/2017].