THE EPIDEMIOLOGY OF BREAST CANCER.

Abstract

Summary A review of available data on the epidemiology of breast cancer indicated the following: ( a ) a remarkable stability of the trend of mortality from female breast cancer in the United States since 1930; ( b ) Japan has the lowest death rate for female breast cancer, and Japan and Finland for male breast cancer, in the world; ( c ) the logarithm of the age-specific death rates from female breast cancer can be resolved into two linear components with the slope of the rates prior to 40–45 years of age being greater than the slope of those after 40–45 years of age; a similar change of slope, although to a lesser degree was observed for males. It was noted that for females this age group corresponded to the time of menopause; ( d ) female patients with breast cancer were more frequently never married or, when married, married at a later age than women in general. Since female breast cancer patients more often gave a history of having had artificial menopause and single women had had artificial menopause less frequently than married women, it was hypothesized that the single-married differences may reflect the differences in frequency of artificial menopause among single and married women; ( e ) the inverse relationship between frequency and length of nursing with female breast is far from being conclusive; ( f ) studies show that females with benign breast disease have an excess risk of developing breast cancer, but more definitive studies are needed; ( g ) studies show the existence of familial aggregation of breast cancer among both males and females; ( h ) a study of male breast cancer patients indicated that a larger proportion of them had a history of orchitis, orchiectomy, therapeutic x-ray exposure and benign breast disease. These data were interpreted as suggesting the influence of hormonal factors as being of importance in the etiology of breast cancer, but more definitive and precise studies are needed. A program of epidemiological research was outlined emphasizing the need for integrating laboratory investigations with the field epidemiological studies.