Deprivation level and the risk of colorectal cancer by anatomic subsite in Northern England

Background: evidence suggests that the incidence of many cancers including bowel cancer vary according to socioeconomic status and education. In case of colorectal cancer, the direction of this association might be even different for anatomical subsites. The aim of this study was to describe the variation in the incidence of colorectal cancer by subsites across North of England and correlate it with community deprivation. Methods: Incidence data were obtained from a population- based cancer registry for the period 1976-2000. Small areas were characterized by their affluence or lack of it, by deriving a Townsend score for each Enumeration District from the 1991 census. The age-standardized incidence rates were calculated for different sites of colorectal cancer for each fifth. The association of each fifth with incidence was also studied using Poisson regression. Results: in men, the age standardized incidence for rectal cancer ranged from 18.3 (for fifth 1, most affluent) to 22.3 (for fifth 5, most deprived) but the trend for proximal cancer was reverse (9.4 for fifth 1 and 8.8 for fifth 5). Poisson models showed a significant inverse association between deprivation level and proximal cancer in both genders. Rectal cancer had a positive significant association with deprivation level in men (RR+1.25, 95% CI, 1.19-1.32). Conclusion: the association of socioeconomic status with proximal cancer was different from that with rectal cancer. Socioeconomic status is not a direct risk factor and might consider as a proxy for life style factors. This indicates that lifestyle correlates of different subsites of bowel cancer differ. Therefore, the different sites of CRC should not be combined in aetiological studies.