Social class as a prognostic factor in breast cancer survival.

The effect of social class on survival of female breast cancer patients was studied by linking the patient files of the Finnish Cancer Registry (FCR) with the information on patient's social status, obtained from the 1970 Population Census of Finland. The material consisted of 10,181 patients 25 to 69 years of age at diagnosis, whose cancer was diagnosed between 1971 and 1980. The classification of social class was based on occupation. The effects of social class, age, period of diagnosis, and stage of disease on survival were evaluated using the Cox proportional hazards model; mortality from causes of death other than breast cancer was taken into account using the exact causes of death. Those in the lowest social class had about 1.3 times higher relative excess risk of dying than those in the highest social class. The older the patients, the greater was the difference in survival by social class. Differences in stage distribution explained only a minor proportion of the variation in survival by social class. The Finnish legislation guarantees everyone fairly equal accessibility to health care. The results suggest that more determined efforts should be undertaken to reduce inequity in survival.