Epidemiologic features of breast cancer in Slovenia, 1965–1967

Abstract

As part of an international collaborative investigation, the epidemiologic characteristics of breast cancer in Slovenia have been studied. An attempt was made to interview all cases of the disease newly diagnosed during a period of 39 months. For comparison purposes, hospital patients with other diseases were interviewed. A total of 806 eligible breast cancer cases were ascertained and 772 were interviewed. Two thousand three hundred and thirty-two control patients were selected and 2308 interviewed. The incidence of ascertained cases was quite similar to that obtained from the data of the Cancer Registry of Slovenia, the rates being approximately twice as high as those in Japan and other Asian populations, but substantially lower than those in North America and Northern Europe. In regard to both the overall level of incidence and the characteristic shape of the age-incidence curve, the data from Slovenia were similar to those from Athens, Creece — the other Southern European center in the international study. There were no significant differences between cases and controls in socio-economic status, number of fetal deaths and frequency or duration of lactation. Even though some patients reported unusually prolonged lactation experience these were equally frequent among the cases as among the controls. Women first pregnant under the age of 25 had approximately 70% of the breast cancer risk of those whose first pregnancy was delayed until age 30 or older. While this trend is in the same direction as that seen in some other centers, the protective effect of early pregnancy seems substantially less in Slovenia than in the other areas studied. There was a significant association between early menarche and increased breast cancer risk. Median ages at menarche were quite late both in the cases and in the controls, similar in fact to those reported in the counterpart study in Japan. There was also an indication that late menopause was associated with increased breast cancer risk. The breast cancer patients were taller and heavier than the controls.