Breast cancer (ICD-9 174)

In females the highest incidence rates were seen in Iceland, Denmark (700-737/10⁶), and in southern Sweden. The rate in Belarus, Russia and Baltic countries was below 350/10⁶. The variation in mortality was much smaller, with the highest rates exceeding 200/10⁶ in Denmark, in western parts of Germany and in Iceland. A slight urban excess was seen in the eastern half of the map.

The mortality incidence rate ratio was lowest (around 0.3) in Finland, Iceland and Sweden, and highest (over 0.5) in Lithuania.

There was a steep increase in the age-specific incidence rate between the ages of 30 and 45 in all countries. Thereafter, a decrease in incidence was seen in Belarus and Baltic countries but a slight increase in the other countries. In mortality, there was a similar age pattern but on a lower level and postponed by 5-10 years.

Breast cancer among men is very rare and data were not collected from all countries. The highest incidence rates (4/10⁶ or more) were observed in the westernmost countries and also in other aspects the map, even if subject to marked random variation resembles that of women.

Hormonal factors including parity and age at first delivery affect the risk of breast cancer. In addition to that the level of diagnostic activity has an influence upon the incidence of breast cancer. A countrywide mammography screening took place only in Finland and Iceland and started towards the end of the observation period (1987-88). Thus, screening can only cause a minor excess in the incidence rate of the screened age-groups (50-59 years).