Trends in European breast cancer incidence and possible etiology.

In this study the trends in breast cancer incidence in a number of European countries, over the last 20 years, have been evaluated. There is a wide range in incidence; the risk being highest in north and west Europe (and highest in Switzerland) and lower in south and in east Europe. There was little difference, however, between countries in the incidence of the disease occurring before the menopause, and this incidence has shown little temporal change in the time period 1960-1985. Indeed, in many countries there has been little change in incidence in any age band since 1975. The use of oral contraception has been claimed to be a risk factor in premenopausal breast cancer. In two countries, the data on oral contraceptive usage were available; in neither was there any evidence that the introduction and growth in such usage was related to the risk of breast cancer in any age band that might have been exposed to them. The reasons for this are discussed in the light of recent reports to the contrary.