history (genetics). Identified gene mutations represent
a tiny fraction of all breast cancers, "much less than
10% overall." But if present, they "confer considerable
life-time risk ... compared to the general population."
and hormonal life, e.g., early menarche, not having
been pregnant or late age at first birth, late menopause,
hormonal factors such as high levels of free estrogen; long-term
use of oral contraceptives or menopausal hormone replacement,
or other factors that increase life-time exposure to estrogen.
"Risk of cancer is influenced by the endogenous hormonal
particularly diet. "High intake of fruits and
vegetables is probably associated with a slightly reduced
risk of breast cancer." Rapid growth and/or high body
mass are risk factors, thought to be related to high total
caloric intake, particularly if not balanced by caloric expenditure.
Meat consumption is possibly associated with an increased
risk, as is alcohol consumption. The impact of tobacco smoke
is even less clear. Most studies examining physical activity
indicate a slight reduction in risk with more activity.
"Only limited data are available on specific exposures
in relation to breast cancer." Studies of the aftermath
of atomic explosions in Japan reveal an increased risk of
breast cancer, "particularly for women having been exposed
around puberty." A few studies show elevated risk in
relation to exposure to electromagnetic fields. With respect
to chemicals, "Suggestive associations were found for
styrene, several organic solvents, such as methylene chloride,
carbon tetrachloride, formaldehyde, as well as for several
metals, metal oxides and acid mists." But some surprisingly,
"systematic reviews on occupation and breast cancer are
stil few and much work remains to be done. Little evidence
is available on virus exposures, although in mice a virus
is a recognized cause that is transmitted from mother to daughters
and endocrine disruptors. Because of the established
role of life-time estrogen levels as a breast cancer risk
factor, considerable attention has been paid to possible impacts
of exogenous estrogens on risk. Long-term use of oral contraceptives
is associated with a small increase in risk.
of organochlorines show contradictory results. Older studies
of PCBs and DDE found higher levels in breast-cancer patients
than controls, but newer, larger studies contradict this (see
also Gammon et al
2002, published since Sasco wrote her review). It
is important to note (which Sasco does not, that the persistent
PCBs and DDE measured in these studies are not xenoestrogens,
but instead anti-estrogens and anti-androgens, respectively.
Thus negative findings with them are irrelevant to the hypothesis
that xenoestrogens elevate breast cancer risk. More...
organochlorine, dieldrin, is associated
with an increase in risk and an increased mortality rate once