Organized Breast Cancer Screening Programs in Canada

1999 and 2000 Report

Background

With 21,100 new cases and 5,300 deaths estimated for 2003, breast cancer continues to be the most common cancer and the second highest cause of cancer death in Canadian women¹. A rise in the incidence of breast cancer has been observed over several decades; this parallels an increase in mammographic screening. However, mortality rates have dropped, particularly since 1990, a decrease attributed, in part, to improved treatment and early detection resulting from mammography screening (see Figures 1a and 1b). The estimates for 2003 represent a projected increase of 9.9% in incident cases and a 3.6% decrease in deaths when compared with estimates for the year 2000². The incidence of and mortality due to breast cancer place a significant cost on society. Hospital expenditures for breast cancer were estimated at $84.8 million in 1998. Mortality costs, which measure the value of life lost due to premature death, were much greater at an estimated $1,062.8 million and represented 10% of the mortality costs associated with all cancers combined³. 

Nearly half of all breast cancer cases occur in women aged 50-69 and it has been demonstrated that these women benefit the most from breast cancer screening.

While the body of knowledge surrounding the causes of breast cancer continues to grow, primary prevention strategies to reduce incidence in the population are currently limited. Most known risk factors are not modifiable; these include demographic factors (e.g. age, country of birth, socio-economic status), genetic factors (e.g. family history, BRCA1 and BRCA2 genetic mutations), hormonal factors (e.g. age
at first pregnancy, age at menarche, age at menopause, parity) and biological factors (e.g. benign breast disease confirmed by biopsy). Of these, age has the strongest influence^4,5. Both incidence and mortality rise sharply with age, the highest rates being found among women aged 60 and over¹. Nearly half of all new cases occur among women aged 50 to 69¹. Women in this age group benefit the most from breast screening, as has been demonstrated through randomized trials. For this reason, the delivery of regular, high-quality breast screening to this group has the potential to reduce breast cancer mortality rates by as much as one-third^6,7. 

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