Breast cancer incidence and mortality. Aspects on aetiology, time trends and curability

Breast cancer incidence is decisively influenced by life style, which probably to a large extent accounts for the more than fivefold international differences in incidence. Hence breast cancer is a potentially preventable disease. The lifetime risk of having a breast cancer diagnosed approaches 6% in the high-risk Nordic countries where the disease constitutes one-fourth of all malignant diseases in the female. A trend towards increasing incidence over several decades suggests a continuing addition of causative environmental agents affecting primarily the risk after the menopause. A constant mortality despite increasing incidence figures seems to be due to earlier diagnosis or a trend towards tumours with a lower malignancy potential rather than to therapeutic improvements. Breast cancer patients show an excess death rate also after 20 years of observation. Recent studies have, however, suggested the existence of a cured fraction constituting about 35% of all cases. The disease has also shown a more favourable prognosis in younger patients.