Incidence and Mortality
Breast cancer is the most common invasive cancer in women worldwide, with almost 1.5 million women diagnosed in 2010 alone. Globally, 1 in 10 women will develop the disease at one point in their lives, with that proportion increasing to 1 in 8 in North America, the UK, Australia and New Zealand. In the USA alone, every day there are 527 new cases of breast cancer diagnosed, with 110 women succumbing to the disease. The higher incidence of breast cancer in women rather than men (~100 times less prevalent in men) is partly because there are far more breast cells in women, but mainly because of the growth-inducing effects of the hormones oestrogen and progesterone.
Risk Factors
The risk factors for a predisposition to develop breast cancer can be inherent or lifestyle-related. Inherent risk factors which have a strong effect on developing the disease include gender, age and genetic factors, but ethnicity can also play a role. Lifestyle-related factors largely reflect why the incidence of breast cancer is higher in Western countries; these include delaying child bearing age, menopausal hormone therapy, fewer pregnancies, alcohol consumption, lack of physical exercise and obesity.
Types of Breast Cancer
There are several different types of breast cancer, the most commonly diagnosed being invasive ductal breast cancer (IDBC), which affects the cells surrounding ductal tissue and accounts for 70-80%. Ductal in situ cancer (DISC) affects the same tissue area as IDBC but is much less aggressive and treatment can be avoided. Other aggressive cancers include lobular breast cancer (ILBC), which is diagnosed in 10% of cases and inflammatory breast cancer (IBC), which presents in 1-2% of cases.
Prognosis
Relative to Western Europe and North America, mortality rates for breast cancer in Asia, Latin America, Eastern Europe and Africa are much higher. In many cases this is due to limited availability of detection services and treatment. The chances of survival after an unfavourable diagnosis largely depend upon the stage to which the cancer has progressed to, with early diagnosis almost always being advantageous. The five-year relative survival rates for women diagnosed with breast cancer in 2001-2006 reached 82% (England only) compared with only 52% from 1971 to 1975. In the United States that figure is currently around 89%. The decrease in mortality in the West can be attributed to the implementation of mammography-screening programs and a reduction in hormone replacement therapy.
