A new study issued by the American Cancer Society (ACS) this week states that breast cancer rates began falling long before the suspension of hormone replacement therapy (HRT) -- and the study credits mammography screening with contributing to the decline.
The report sheds additional light on the report issued in December 2006 by researchers from the University of Texas M. D. Anderson Cancer Center in Houston. The study found that there was a 7% drop in the incidence of breast cancer in the U.S. in 2003.
News reports at the time attributed the decline to the suspension of HRT, which was halted for millions of women after research surfaced linking HRT to a slight increase in breast cancer risk.
In the new study, ACS researchers used a large national database to examine breast cancer rates in women 40 and older between 1975 and 2003. Factors they examined included tumor size, stage, and whether tumors had receptors for estrogen (ER-positive) or progesterone (PR-positive).
The ACS study found the same sharp decline in breast cancer cancers as detected by the M. D. Anderson researchers, with the decline greatest among women 50-69 years old -- those most likely to be on HRT. But the researchers also found that breast cancer rates, especially for small tumors, actually started declining in 1999 -- long before the link between HRT and breast cancer became known.
The ACS believes that the reason behind the earlier decline is that mammography use leveled off at about this time, after increasing steadily for 12 years. The society believes that if mammography use goes down, that means fewer breast cancers are being found. When mammography use goes up -- as it did between 1980 and 1998 -- breast cancer rates rise, leading to a 40% increase in rates during the period.
The ACS study concludes on a cautionary note, stating that the current decline in breast cancer rates could be temporary, the result of delayed detection rather than an actual decrease in incidence. The society reiterated its guidance that women get mammograms every year, starting at age 40.
By AuntMinnie.com staff writers
May 3, 2007
Related Reading
What goes up must come down -- A new look at the 2003 drop in breast cancers, December 22, 2006
Drop in breast cancer tied to less HRT, December 15, 2006
RSNA studies delve deeper into DMIST results, December 14, 2006
Regular mammo screening reduces risk of false-positive results, needless biopsy, August 9, 2006
Sidestepping screening: What factors make women avoid annual mammography? October 10, 2005
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