Does socioeconomic status influence the prospect of cure from colon cancer--a population-based study in Sweden 1965-2000.

AIM OF STUDY: Differences in the survival of colon cancer patients by socioeconomic status have been demonstrated in several populations, but the underlying reasons for the differences are not well understood. By simultaneously estimating the proportion of patients cured from colon cancer and the survival times of the 'uncured' we hope to increase understanding of how socioeconomic status affects survival following a diagnosis of colon cancer.
METHODS: We conducted a population-based cohort study of 58,873 patients diagnosed with colon cancer in Sweden 1965-2000. Socioeconomic status was classified based on occupation. We fitted mixture cure models and Poisson regression models adjusted for age, sex and calendar period.
RESULTS: We observed higher excess mortality, lower proportion cured and shorter survival times among the uncured in patients from lower socioeconomic groups compared to the highest socioeconomic group. There was no evidence that the gap between the socioeconomic groups reduced over time. Farmers had the lowest odds of cure (odds ratio (OR) 0.85, 95% confidence interval (CI) 0.75-0.95) compared to higher non-manual workers followed by self-employed (0.91, 0.81-1.03), manual workers (0.93, 0.85-1.03) and lower non-manual workers (0.98, 0.89-1.08).
CONCLUSION: Patients from lower socioeconomic groups in Sweden experience worse survival following a diagnosis of colon cancer. Differences exist in both the cure proportion and the survival time of the uncured, suggesting that socioeconomic differences cannot be attributed solely to lead time bias.Although this study has furthered our understanding of socioeconomic differences in survival, more detailed studies are required in order to identify, and subsequently remove, the underlying reasons for the differences.