Socioeconomic effects on breast cancer survival: proportion attributable to stage and morphology

Breast cancer patients of lower socioeconomic status tend to have poorer survival. Among 10 865 cases of breast cancer from the East Anglian Cancer Registry diagnosed between 1982 and 1993, we estimated the extent to which the differences in survival by socioeconomic status, measured by both occupational and area-based methods, can be explained by differences between socioeconomic groups in stage and morphological type of tumour. In univariate survival analyses, lower social class (manual occupation) was associated with a relative hazard of 1.32 (95% CI 1.12-1.55) for death from breast cancer as underlying cause. Women resident in the most deprived area had a relative hazard of 1.21 (0.95-1.54) for death from breast cancer as underlying cause. Stage of disease accounted for 28% of the effect of social class on survival but for none of the effect of deprivation category. Morphological type accounted for 3% of the effect of social class and none of the effect of deprivation category. Thus, stage at presentation explains some but not all of the socioeconomic differences in breast cancer survival. Future research on histological grade and socioeconomic status is indicated.