Some international differences in treatment and survival in breast cancer.

In a recent study, 5-year survival rates for breast cancer patients in Boston (Massachusetts), Glamorgan (Wales), Slovenia (Yugoslavia) and Tokyo (Japan) were 57.3%, 49.5%, 41.9% and 74.9%, respectively. In this report, data are presented on the types of treatment used in the four areas and on the relationship of differences in treatment practices to the differences in survival rates. Generally, surgically treated patients who also had radiotherapy had lower survival rates than patients in the same area who had similar operations without radiotherapy. In each area, the survival rate was higher for patients who had radical mastectomy than for those who had simple mastectomy. The Japanese patients had the highest survival rate within nearly every treatment and extent-treatment category. Thus, the high survival rate of these patients was not explained by the variables considered. Survival differences between Boston, Glamorgan and Slovenia were largely explained by differences in extent of disease and type of treatment. As the nature of the treatment--survival trends was consistent with the interpretation that treatment tended to be selected according to apparent prognosis, the degree to which treatment customs were determinants of the differences in survival rate among the three areas is uncertain.