Research by the American Cancer Society (ACS) confirms that the drop from 2002 to 2003 in breast cancer rates correlates with decline in hormone therapy use. However, the research also indicates that the rate of occurrence of breast cancer is related to the leveling off of
But, the organization notes that the decline in breast cancer rate could just indicate that fewer instances are being detected because screenings have diminished.
ACS said that the drop in breast cancer rates occurred fairly recently. From 1980 to 1998, the rates went up sharply--by nearly 40 percent. This occurred as mammograms became more common.
Research unveiled earlier this year showed that there was a steep decline in breast cancer rates from 2002 to 2003 which leveled off the following year. The researchers associated this with the decline in hormone therapy.
The ACS research agrees with the cause of the greatest decline in disease among women 50-69 years old, the population most likely to use hormone therapy.
Yet, quitting hormone therapy can't explain the other major finding from the study, ACS said. The researchers found that breast cancer rates started dropping in 1999 for all women 45 and above, well before the link between hormone therapy and health problems was found.
The most likely explanation for the earlier decline is that mammography use leveled off during those years, after nearly 12 years of increase, ACS said.
But the organization also believes that part of the decline in breast cancer cases may be temporary. This would mean that there has been a delay in detection, rather than an actual decrease in incidence.