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Ethical issues associated with PGD for inherited cancer susceptibility
 This is because of a
combination of several factors:
• they are lower-penetrance (i.e. not everyone with the
faulty gene will develop the cancer);
• the occurrence of cancers have a later age of onset — in
adult life in many cases;
• there is a possibility for preventative surgery, early
detection and effective treatment for these
cancers in susceptible individuals.
Penetrance: The penetrance of a condition determines the
proportion of people who carry a copy of a faulty gene that
will be affected by a condition. If a condition is 100 per
cent (or fully) penetrant, every person who carries a faulty
gene will develop the condition. If a condition is 50 per
cent penetrant, half of the people that carry a faulty gene
will go on to develop the condition.
The penetrance for cancer development of the conditions we
are considering here varies from around 30 per cent to 80
per cent depending on the condition or the fault within the
gene. Carriers of these genes therefore have a strong
likelihood, or predisposition, to developing cancer but not
a certainty.
Age of onset: This refers to the age at which symptoms of
the genetic condition are seen. The majority of conditions
for which PGD have been performed cause illness in the baby
when it is born or in childhood. If a person inherits a
faulty gene that causes a predisposition to cancer, the
person is not likely to be affected by this condition until
they are in their late thirties, forties or fifties.
 The potential for preventative surgery, early detection and
effective treatment: Although there are treatment options
for many of the conditions, for example cystic fibrosis,
these are usually for the relief of symptoms rather than
providing a cure. For people who develop cancer it is
possible to be treated with drugs and/or surgery. Many
people are successfully treated for cancer and this number
is increasing as better treatments are developed. It is also
possible for people who know that they are at risk to have
regular checks and/or preventative – prophylactic – surgery
to remove tissue that is likely to be affected by cancer
such as the breasts (mastectomy) or bowel (colectomy). These
are difficult decisions to make because there is a chance
that the cancer may not develop, and if it does, it could be
treated.
As couples present for PGD of heritable cancer, there is
likely to be widespread debate in the community about the
associated ethical issues, including disposal of embryos
carrying the cancer-predisposition gene mutation and the
practice of eugenics. The ethical issues surrounding PGD for
heritable cancer are really no different from those for
autosomal dominant late-onset disorders. The best example is
Huntington’s disease where individuals with ³40 CAG repeats
in the Huntington gene have many years of ‘disease-free’
life, but will ultimately develop neurological symptoms
later in their lifetimes. Like Huntington’s disease, the
overall life experience of some individuals and families
affected by inherited cancer syndromes is also profoundly
difficult, not only from seeing family members suffer from
the disease but also the anxiety about if and when they too
will be affected. The option of PGD can ensure that future
generations of families who utilise this technology will not
be faced by such difficulty. It also offers an option to
couples who would find terminating a pregnancy for an
adult-onset cancer predisposition syndrome unacceptable.
Couples who choose to utilise PGD do not make this decision
lightly. It can be a long, stressful and costly process, and
only those who are committed to the outcome will persist
with it.
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Protocols available in our Centre
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