Of every 100,000 women in the state aged 50 to 54, a number will discover each year that they have breast cancer. That number is depicted in this graph. (The council presents data on this one age group, rather than on the entire female population, to control for factors such as changes in the average age of the larger population; age 50 to 54 was selected as a representative age group and is used in each year’s report.) To minimize year-to-year fluctuations, groups of years are averaged together. (In other words, each data point on the graph shows the number of new cases in a single year, but that year is actually the average of five years.) While some breast cancers are linked to genetic factors, most are associated with non-genetic factors including diet, reproductive history, lifestyle, and external agents.

Breast Cancer as an Environmental Indicator

There are numerous studies connecting certain chemicals and other environmental factors to breast cancer. These factors, if significant, do not appear to be as important statistically as a woman's own reproductive history, but it is important to note that breast cancer rates vary greatly in different parts of the country. Among the fifty states, Connecticut has the highest incidence of breast cancer; this assessment is based on average incidence rates from 2003 through 2007, the latest years for which 50-state data are available. (Source: North American Association of Central Cancer Registries).

The rate of new cases showed improvement in 2000 through 2004 (using the average of the five years) and has held steady for the four-year period of 2005 through 2008 (the most recent years for which Connecticut data are available).