Social class and weight as prognostic factors in early breast cancer.

Data from the Cancer Research Campaign trial for early breast cancer have been used to study the effect of social class and weight on prognosis after primary treatment either by a simple mastectomy plus post-operative radiotherapy or by a simple mastectomy followed by a watch policy. There were 2455 patients for whom both social class could be determined and weight was recorded. These patients presented in clinical stages I and II and were recruited between June 1970 and April 1975. The cut-off date for the analysis was 31 December 1991. When the survival curves of patients in manual classes were compared with those in non-manual classes, there was a tendency for the latter to do better, but the difference was not statistically significant (P = 0.12). By contrast, there was a highly significant difference (P = 0.002) in survival favouring patients weighing less than or equal to 60 kg compared with those weighing greater than 60 kg. The difference was confined to post-menopausal patients and was still highly significant when included in a multivariate analysis with social class, age, tumour size, clinical stage and tumour grade. The effect of weight was to increase the mortality due to breast cancer rather than other causes.