Screening
mammography reduces a woman's risk of dying from breast cancer,
but it takes a long time for this benefit to become evident, according
to a study published in the journal Lancet.
Screening mammography
refers to mammography performed in women who do not have any signs
or symptoms of cancer. The goal of this test, which is recommended
by many health organizations, is to catch cancers in the earliest
stage, leading to earlier treatment and better odds of a cure. Early
studies suggested that screening mammography saved lives, but many
of these studies had flaws. A recent large study found that death
rates did not differ for women who were and were not having screening
mammography.
At present,
the subject of screening mammography remains controversial. Researchers
in Canada and the United States used a new approach to analyze data
from an earlier study. They focused on a different indicator of
breast cancer deaths, and paid special attention to the later years
of a screening program, assuming that it would take many years before
the lives saved by screening would become evident.
In the first
six years of the screening program, rates of breast cancer death
did not differ between women who were and were not being screened.
However, from the seventh year onward, rates were lower for the
women who were having screening. Among women who had been in the
program for 8 to 11 years, women who were aged 55 years and older
at the start of the study were 55% less likely to die from breast
cancer, and women who were aged 45 to 54 years at the start of the
program were 30% less likely to die from breast cancer. These results
suggest that screening mammography prevents deaths from breast cancer. |