Improvements in childhood cancer survival are testament to important
strides made in treatment and cure. However, prevention is still
a preferable goal since cure does not come without suffering on
the part of the individual child and family.
Preventing cancer is an immense challenge given our relative inability
to pinpoint precise causal factors, particularly for childhood cancers.
We also have to acknowledge that only a small fraction of chemicals
and substances has been adequately tested for carcinogenicity.
Finally, as stated before, cancer is described as a multifactorial
disease involving both environmental exposures and genetic factors.
For that reason, it is often emphasized that cancer is largely preventable.
The fact that etiology is undetermined for most childhood cancers
means, however, that there are few, if any, specific strategies
clinicians can offer patients to reduce the risk of cancer in their
Based on the existing evidence for risk factors in childhood cancer,
avoiding exposure is the most fundamental preventive advice
that can be given to patients.
The patients to target specifically include men and women who are
considering having a child, pregnant women (and their partners)
and the parents of infants and very young children. The clinician
might advise these patients to take a prudent approach and
avoid exposures to some suspected risk factors such as cured meats,
unnecessary x-rays and a variety of chemicals including pesticides,
solvents and paints.
It is apparent that children may be more susceptible to radiation-induced
leukemia as there is a peak of leukemia incidence about five years
after exposure. Where there is potential hazardous workplace exposures,
clinicians may be important advocates assisting patients in reducing
exposure by changes to the work site or modification of duties.
Research is indicating that other behaviours may reduce
the risk of pediatric cancer. For example, a large, international
collaborative study of pediatric brain tumours suggests that the
risk of childhood brain cancer was significantly reduced when mothers
took prenatal multi-vitamin supplements for two or more trimesters
of their pregnancy.100,101
The finding that breastfeeding is correlated with significantly
decreased risk of acute leukemias in childhood, likely due to the
immune-stimulating effects of breast milk, provides yet another
reason that breastfeeding should be vigourously supported as the
optimal method of infant feeding.101,102
Our knowledge of the links between lifestyle choices and cancer
prevention pertains mainly to adults. However, we likely arm our
children with the best possible protection against cancer by instilling
healthy habits during childhood. For example, there are consistent
findings that high consumption of fruits and vegetables, moderation
in red meat, fat and alcohol intake and regular exercise and maintaining
a healthy body weight are all cancer-protective strategies.102
Although most types of cancers are quite difficult to link to the
specific causal exposures (and do not directly affect children),
there is still good reason to prevent exposure to carcinogenic substances
at the youngest ages possible.103 Clinicians
and parents should therefore ensure that a child's exposure to known
carcinogens such as environmental tobacco smoke, asbestos and sunlight
are minimized in order to reduce the risk of developing cancer in
Environment Canada provides forecasts
of the daily ultraviolet (UV) indices for selected Canadian cities.
Health Canada's It's your Health series includes the document
Skin Cancer - It's Up to You.
The Canadian Dermatology Association Web site includes useful resources,
such as Sun
Safe - Tips for Parents and Teaching
Pre-schoolers SUNSAFE Play, Everyday! - Tips for Daycares.
Research on immune system effects in people from environmental
exposures is clearly in its infancy. The number of substances known
to be immunotoxic is relatively small, but may only represent the
proverbial tip of the iceberg. As such, personal prevention is difficult
to achieve. Avoiding certain exposures is virtually the only advice
that can be given to patients.
As with cancer, the patients to target specifically include men
and women who are considering having a child, pregnant women (and
their partners) and the parents of infants and very young children. The clinician might advise these patients to take a prudent approach
and avoid exposures to the few risk factors for which evidence of
immunotoxicity is accruing.
In particular, people are well advised to avoid certain practices
- Use of pesticides, especially those that are sprayed and/or
applied indoors. Spraying and indoor application are both associated
with greater exposure of pesticides to humans and pets.
- Consumption of sport-caught fish (especially in the Great Lakes
region), which is associated with much greater intake of persistent,
bioaccumulating, biomagnifying contaminants and, therefore, is
not advised for women in their childbearing years, nor children
under fifteen. Others should, at a minimum, follow the provincial
guides to sport fish consumption to determine which are the least
contaminated fish and appropriate ways to prepare such fish. They
should also be mindful of special advisories that notify the public
of unusual episodes of contamination. (For example, see the Ontario
Ministry of the Environment for fish consumption guidelines
Although there has been increasing evidence of the presence of
POPs in breast milk, breastfeeding
is still to be advocated as the optimum way to nourish babies since,
by what science knows so far, the benefits of breast milk far
outweigh the risks from exposure to contaminants in breast milk.104,105
Personal prevention represents only one aspect of reducing cancer
risk in children. Clearly, when exposures to carcinogens and immunotoxins
in the environment most often occur unknowingly and involuntarily,
we should strive for greater focus on primary prevention. Specifically,
government policies and standards that are informed by current,
comprehensive testing of environmental agents will ultimately be
the most effective strategy for protecting children from cancer
and immunotoxic exposures.
This includes a strong government stance and action to reduce POPs,
for instance, in the environment internationally. In the wake of
the report of the House of Commons Standing Committee on Environment
and Sustainability that made numerous recommendations to reduce
pesticide use in Canada, there has still been little substantial
action to further those recommendations.