Inequalities In Colorectal Cancer Risk And Prognosis In Victoria, Australia

Roger MILNE, Cancer Council Victoria, Australia

1 Cancer Epidemiology Centre, Cancer Council Victoria, Melbourne, Australia
2 Victorian Cancer Registry, Cancer Council Victoria, Melbourne Australia

Purpose: Assess inequalities in colorectal cancer (CRC) incidence and outcomes by sex, socio-economic status (SES) and geographic remoteness using population-based registry data.

Methods: Incident cases diagnosed between 2004 and 2013 were identified through the Victorian Cancer Registry and linked to the state death registry up to 31st December 2014. SES and remoteness were determined from the population census. Associations with incidence were assessed by multivariable Poisson regression. Associations with survival were assessed by multivariable Cox regression.

Results: Overall 35,638 incident cases of CRC were ascertained, 15,540 of whom died during median follow-up of 3.2 years (interquartile range: 1.4-6.0). Average CRC incidence per 100,000 was higher in men (45 versus 31), in persons with lower SES (41 for lowest quintile [Q1] versus 34 for Q5) and in those living outside major cities (41 versus 36). The association with SES was stronger for men. The association with remoteness was not apparent for people with higher SES. Male cases, and cases with higher SES, were more likely to be diagnosed with early stage disease.
Men with CRC had worse prognosis (HR for all-cause death, 1.22 [95%CI, 1.16-1.27]) as did cases with lower SES (HR for Q1 versus Q5, 1.44 [1.33-1.55]); the latter appeared to attenuate with increasing time since diagnosis (p=0.035). A survival disadvantage for non-metropolitan cases observed in univariable analysis was largely accounted for by SES. These associations were independent of disease stage and grade, age at diagnosis and calendar year.

Conclusions: Sex, geographical remoteness and SES interact as determinants of CRC risk in Victoria. Sex and socio-economic inequalities are also apparent in outcomes for people who develop CRC, which appear to be unrelated to disease stage and grade at diagnosis. Further work is required to understand and address these disparities.

Funding sources: Cancer Council Victoria, Victorian State Government