The recent decline in invasive breast cancer in the US was significantly less pronounced in the poor and those who live in rural areas. Researchers suggest this may be due to varying reductions in the numbers of women taking hormone therapy (HT).
Christina Clarke, Ph.D., led a team of researchers from the Northern California Cancer Center who studied breast cancer incidence data from the largest cancer database available in the US for the years 1997-2004, comparing poor areas against rich and urban areas against rural.
She said, "Between 2001 and 2004, incidence rates of invasive breast cancer declined more than 8% in the United States. "One possible explanation for this is widespread discontinuation of and/or failure to initiate HT. Because this cessation of HT use was more pronounced in rich/urban areas, we wanted to see if there was a corresponding difference in breast cancer incidence between these areas and poor/rural parts of the country".
The researchers found that overall invasive breast cancer incidence fell 13.2%, with greater reductions among women living in urban (-13.8%) versus rural (-7.5%) and low- (-13.0%) or middle- (-13.8%) versus high- (-9.6%) poverty counties. Breast cancer incidence trends for rural counties, which peaked in 1999 and then declined steadily, differed from those observed in urban counties, where rates fell dramatically after 2002. The researchers speculate that this may be due to variations in exposure to the news that HT was associated with breast cancer, they cite a 2007 report that found that the number of newspaper articles about the harmful effects of HT found in the 2002 Women's Health Initiative (WHI) trial correlated with urban residence and likelihood of HT cessation/non-initiation; women in urban areas were potentially exposed to more newspaper articles and had a larger decline in the prevalence of HT use.
Dr. Clarke added that "Understanding what specific populations were involved in the breast cancer declines helps us to better plan prevention efforts for the future, especially with the aging of the baby boomer population into prime breast cancer age."
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