PE: What
are the obstacles in patient education about prevention? Dr. Mai: First, I
think we need some very good research to help us along; for example,
what does it take to adopt healthy behaviours? Many people know
what s good for them, but making the behavioural change is the hard
part. We need to find ways to facilitate such lifestyle changes
-- some have called this putting in place supportive environments.
Dr.
Eisen: The reasons why people now are eating too much and
not exercising enough are complex. There are no easy answers, making
counselling a challenge. Also, you re not necessarily going to feel
better tomorrow as result of a healthy lifestyle choice today, so
there s no instant gratification. it's also difficult to get such
changes adopted by children and young adults -- and that s clearly
the area where these modifications will have the strongest impact.
PE: Have
we learned any lessons from anti-smoking campaigns? Dr. Mai: I think we've learned that you need to tackle things from a number of directions.
For one, it's important to ensure that people have the pertinent
health information. But then there are also population strategies:
making healthy choices available and unhealthy ones unavailable,
which can be achieved at the policy level. we've learned from our
work on tobacco for instance, that we have to reinforce the same
message on many fronts.
PE: How are
prevention and screening related? Dr. Eisen: These two
entities are often lumped together because the goal of both is to
reduce morbidity and mortality from cancer, but obviously there
are differences. For prevention, the goal is to have interventions
on the population level or on the individual level that prevent
the occurrence of cancer. And the goal of screening is to detect
cancer at an early stage when it's more treatable and more curable.
Dr.
Mai: There s some association between prevention and screening,
as some of the tests detect pre-cancerous lesions. If these cells
are removed or treated, you ll be preventing cancer. Take the various
abnormalities found on Pap tests, for example -- if treated, they
never grow into a tumour. In this light, it probably makes sense
to integrate approaches that deal with both prevention and screening,
especially when you re giving advice to patients.
PE: What
screening procedures are recommended? Dr. Mai: There are
currently 3 proven screening approaches for the general public:
the Pap test for cervical cancer, breast screening with mammography
for women age 50 to 69, and colorectal screening, which is the newest
one to come along, with good evidence for recommending it to all
people between 50 and 74 years old.
Dr.
Eisen: People who are genetically predisposed to cancer are
a special case. For instance, women at the highest risk for breast
cancer have a lifetime risk that is at least 60%, which is much
higher than that for the general public. The average age at diagnosis
is also much younger for these individuals. So if they're interested
in screening as a preventive strategy, we recommend starting earlier
-- at about the age of 30. We also suggest mammography and
MRI scans of the breast. The most radical, but also most effective,
option is to have both breasts removed preventively.
PE: Do we
know how our genes interact with the environment? Dr. Knight: Some people
believe that a lot of cancers are due to interactions between genes
and the environment. This means that there s hope, i.e. that if
we can better understand which genes and which environmental factors
are implicated, we ll be able to develop more targeted therapies
or prevention strategies. The relationships are tricky to disentangle,
but it's a very hot area of research right now. I ve been looking
at alcohol metabolism, which is to some degree genetically controlled,
so it might influence breast cancer risk or the risk for other cancers
that show a connection with alcohol.
Dr.
Eisen: We're not at the point yet where we can test someone
s blood and say, "Oh, you have this genetic profile so go ahead
and smoke or go ahead and drink; you ll be OK". In the hereditary
breast cancer group that I see (BRCA1 and BRCA2 mutation carriers),
not everybody gets cancer although their risk is quite high. The
question is, why do some individuals who carry the same mutation
develop cancer and others don't ? Is it that they have some protective
genetic factors? it's not quite clear. We re still at the stage
of trying to delineate that.
