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Difficulties in Translating Relative Risks Into Absolute Risk

Difficulties in Translating Relative Risks Into Absolute Risk

PARIS--When counseling women about breast cancer risk, physicians
face the difficulty of translating relative risks into real-life
prospects, Michael Baum, CHM, FRCS, of the Royal Marsden Hospital,
London, said in a presentation at the Eighth Annual European Cancer
Conference (ECCO-8).

The lay public's perception is that about one in 12 women will
develop breast cancer at some point in life, Prof. Baum said,
and, thus, a woman who is told that she has a threefold increase
in risk may go through life believing that her chances of developing
breast cancer in any one year are 25%.

"This is cruel and we have ourselves to blame for all the
fear that's out there in the community," he said. "The
public has difficulty in translating relative risk into absolute
risk."

Prof. Baum's counseling strategy is to advise women not to think
about their lifetime risk, but about what may happen in the next
decade. For example, he said, a normal 50-year-old woman has a
2% chance of developing breast cancer over the next decade, and,
thus, even a threefold increase in the odds means only a 6% risk.

"Counseled that way, most of my patients can live with that
risk without being forced into inappropriate and experimental
risk avoidance schemes," Prof. Baum said.

It may be more difficult, he acknowledged, to counsel the young
patient with a suggestive family history. He noted that computer
programs are now available that can calculate the probability
of penetrance of a dominant gene.

A woman with a family history of breast cancer may have a rare
inherited gene with a high penetrance, such as BRCA1, BRCA2, and
p53; a common inherited gene with low penetrance; or sporadic
mutations due to an inherited deficiency of DNA repair mechanisms,
Prof. Baum commented.

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