Deprivation gap in colorectal cancer survival attributable to stage at diagnosis: A population-based study in Spain

Objective: Socioeconomic inequalities in colorectal cancer (CRC) survival are a major concern of the Spanish public health system. If these inequalities were mainly due to differences in stage at diagnosis, population-based screening programs might reduce them substantially. We aimed to determine to what extent adverse stage distribution contributed to survival inequalities in a Spanish region before the implementation of a CRC screening program. Methods: We analyzed data from a population-based cohort study that included all patients living in a region of southern Spain with CRC diagnosed between 2004 and 2013. The European Deprivation Index was used to assign each patient a socioeconomic level based on their area of residence. The role of tumor stage in survival disparities between socioeconomic groups was assessed using a causal mediation analysis. Results: A total of 2802 men and 1957 women were included in the study. For men, the adjusted difference in deaths between the most deprived and the most affluent areas was 131 deaths per 1000 person-years by the first year after diagnosis. Of these deaths, 42 (per 1000 person-years) were attributable to differences in stage at diagnosis. No socioeconomic disparities in survival were detected among female patients. Conclusions: In this study, we mainly detected socioeconomic disparities in short term survival of male patients. More than two thirds of these inequalities could not be attributed to differences in stage at diagnosis. Our results suggest that in addition to a screening program, other public health interventions are necessary to reduce the deprivation gap in survival.