The extraordinarily high rate of breast cancer reported rece Marin County Breast Cancer Rates Flawed (dateline June 1, 2003) | Breast Health News | Imaginis - The Women's Health & Wellness Resource Network

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Marin County Breast Cancer Rates Flawed (dateline June 1, 2003)

The extraordinarily high rate of breast cancer reported recently in Marin County, California was due to faulty data, according to the National Cancer Institute. The Northern California Cancer Center had reported the average number of new breast cancer cases in Marin County to be 199 out of 100,000 white females from 1995 to 1999, compared with 143 per 100,000 white females for the rest of urban California. This represented a 20% higher rate of breast cancer in Marin County, compared with the U.S. population in general. While National Cancer Institute researchers cautioned that breast cancer is still a serious concern for Marin County, as it is for the country in general, the originally reported rates were not correct.

The Northern California Cancer Center had reported high rates of breast cancer in Marin County, beginning in the 1990s, when it said that the rate of breast cancer rose 37% during the decade compared to just 3% in the rest of the United States. In a 2002 paper published in BioMed Central’s Breast Cancer Research, Christina A. Clarke of the Northern California Cancer Center and colleagues suggested that the high rates of breast cancer in Marin County might be due to the type of women residing in Marin County; namely, educated, middle class women. These women tend to have children later in life, which increases the risk of breast cancer.

Others blamed some environmental factor for the sharp increase in breast cancer rates in Marin County, though nothing specific had been identified. Additional theories included the stress of work, pesticides used on lawns, chemicals present in plastic bottles of water, a San Rafael quarry, a plastic foam cup factory in Corte Madera, and the county’s power lines.

However, the National Cancer Institute recently announced that the very high rates of breast cancer reported in Marin County were flawed because they were based on 1990 census data, which underestimated populations of women in high-risk categories. Census data reported from 2000 caused the National Cancer Institute to revise estimates, which they plan to release in mid-April. According to the Institute, breast cancer rates in Marin County are likely due to the county’s population demographics more than an environmental influence.

The new estimates are in line with breast cancer rates in other affluent counties of California, which are still higher than the national average, making it a serious concern. Breast cancer rates have also been reported to be exceptionally high on Long Island, New York. Again, environmental factors had been blamed. However, a $30 million federal study found no link between pollution or the environment and breast cancer rates on Long Island.

For the whole of the United States, breast cancer is the second leading cause of cancer deaths in women today (after lung cancer) and is the most common cancer among women, excluding nonmelanoma skin cancers. According to the World Health Organization, more than 1.2 million people will be diagnosed with breast cancer this year worldwide. Though all women are at risk of developing breast cancer, the disease tends to strike older women more often than younger women. Approximately 77% of breast cancer cases occur in women over 50 years of age.

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