Hormones Cause More Than Angst
& Genetic History May Amplify Breast Cancer Risk
puberty a cancer risk? A study of female twins published in The
New England Journal of Medicine found that puberty may increase
the risk of breast cancer in women who carry a genetic predisposition
to the disease.
portion of women who develop breast cancer have known genetic abnormalities,
such as BRCA mutations, that raise their chances of getting the
disease. Not much is known about what other factors work together
with genetic mutations to cause cancer in breast cells.
Ann S. Hamilton and Thomas M. Mack reasoned that breast cancer must
be influenced by other factors. In a Reuters Health interview, Hamilton
explained, "We still have a lot to learn about breast cancer
and the genetic factors that have been identified so far do not
account for all the cases of breast cancer thought to be associated
with genetic susceptibility."
cause of breast cancer is thought to be excessive lifetime exposure
to ovarian hormones such as estrogen. Perhaps the onset of puberty,
menopause and age at first pregnancy might interact with the genetic
history to affect the risk.
examined 1,811 pairs of twins where either one or both of the twins
had breast cancer. They looked for links between age at puberty,
menopause and pregnancy and onset of breast cancer.
where both developed the same type of breast cancer, disease-concordant
twins, were assumed to have a hereditary predisposition, genetic
mutations, that raised their risk.
found that, in these pairs, the first twin to reach puberty was
five times more likely to get breast cancer earlier.
with nonhereditary breast cancer, where only one of the twins had
been diagnosed with breast cancer, showed no relationship between
the age of puberty and breast cancer risk.
this group, the twin that had a later first pregnancy, fewer children,
and later menopause showed an increased risk of breast cancer. In
the twins where both developed breast cancer these factors did not
seem to make a difference.
researchers concluded that, "within the most genetically susceptible
subgroup of twin pairs, the strong influence of earlier puberty
on the age at the diagnosis of breast cancer and the absence of
linkage to hormonal milestones later in life suggest that most cases
of hereditary breast cancer are not related to cumulative hormone
exposure and that they may instead result from an unusual sensitivity
to pubertal hormones."
does this mean to women who are at high risk of breast cancer?
verifies that the genetic predisposition to breast cancer is affected
by other factors. Earlier exposure to estrogen in the twin who reached
puberty first meant earlier onset of breast cancer. Perhaps preventive
treatments could be designed to interfere with the early effects
of estrogen in women with hereditary breast cancer.
adds concern about the increase in childhood obesity. Fat tissue
may increase the effects of estrogen. If the hormones introduced
at puberty affect the risk of developing breast cancer, then heavier
girls are increasing this risk.
adds one more piece to the puzzle of what causes breast cancer.
Eventually there will be enough pieces to see the whole picture
and design interventions to stop breast cancer before it starts.
England Journal Of Medicine June 5, 2003 Vol 348,23 pp. 2313-2322
on the Web:
Cancer Link To Puberty?
Suggests Puberty-Breast Cancer Link
breast cancer clues
Puberty Linked to Breast Cancer
July 15, 2003
Last updated July 23, 2006