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Rates of mammography in the United States may be falling, a new study shows. Rates fell from 70% to 66% between 2000 and 2005, and the researchers say that this may explain some of the apparent recent decline in the incidence of breast cancer (Cancer 2007 May 14 doi: 10.1002/cncr.22723).
Possible reasons for the decline in mammography include an increase in the number of women who do not have health insurance, reduced perceived risk because of reports of decreasing mortality from the disease, and a lack of emphasis on mammography in health promotion campaigns.
“These 2005 estimates signify the first time that nationally representative data have shown a significant decline in the use of mammography in the US and they are distributed throughout the groups for which screening is recommended,” say the authors from the National Cancer Institute and the Centers for Disease Control and Prevention.
The authors assessed trends in mammography rates from 1987 to 2005 and then used estimates from the 2000 and 2005 national health interview survey (NHIS) to characterise trends and current patterns in mammography use.
They say that between 1987 and 2000, the percentage of women older than 40 years who reported that they had had a mammogram in the previous two years rose from 39.1% to 70.1% and had already exceeded the US government's Healthy People 2010 target of 70%.
But the results also show that estimated mammography rates were 3.8% lower in 2005 compared with 2000. The largest drops were among women who traditionally have used mammography at high rates, including women aged 50-64 years and women with higher incomes.
The researchers say that the drop could be caused by a number of factors, including screening being less desirable because of perceived inconsistencies in the effectiveness of mammograms to prevent deaths. Other possibilities include rising malpractice litigation against radiologists who read mammograms, and fewer radiologists choosing to specialise in breast imaging.
The report says that changes in screening rates have an immediate effect on the reported incidence of breast cancer and mortality. It says that when rates of screening drop, women who are diagnosed as having breast cancer who had stopped screening will be detected clinically later than if they had continued screening, resulting in a short term drop in incidence.
The researchers say that the Annual Report to the Nation on the Status of Cancer shows a levelling and possible decline in the incidence of breast cancer in 2003.
“This decline occurred over approximately the same period as the decline in the use of mammography,” they say. “Consequently, we are concerned that some of the observed decline in incidence may be caused in part by the levelling off and reduction in mammography rates. If future NHIS data continue to show a decline in mammography use, then, as a nation, we need to be prepared to address it.”