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Smaller tumours more aggressive
past 70
Contrary to common wisdom that
tumour aggressiveness slows with age, some breast
cancers actually worsen in women over 70, according
to Belgian researchers presenting to the European
Breast Cancer Conference in Berlin. The likelihood
of spread to the lymph nodes decreases as a woman
ages, but once she passes the 70 year mark, the
odds of lymph node involvement doubles with every
decade — but only if the tumour is no more
than 15mm across. For growths larger than 40 mm,
aggressiveness continues to decline with age.
The authors speculate that their
observations reflect a decline in the women's
immune defence that goes hand in hand with aging.
While tumour aggressiveness may continue to lessen
with advanced age, this effect could be offset
— especially for small tumours — by
a weakened immune response in the above-70s.
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The guidelines are quite specific
on how often women should be screened for breast cancer
— at least once every two years until the age of
70. But what happens after 70? So far, there have been
no clear recommendations. "After age 70, it's basically
left up to the physician what kind of screening to recommend,"
says Dr Ellen Warner, medical oncologist at the Odette
Cancer Centre in Toronto.
This may soon change, however.
Two major new studies have found clear benefits when
women continued to go for regular mammograms after 70.
The first study, published ahead of print April 21 in
the Journal of Clinical Oncology, evaluated breast
cancer diagnoses in more than 12,000 women over 80 and
related the stage of the cancers to how regularly the
patients had gone for mammograms during the preceding
60 months. The second study, presented at the European
Breast Cancer Conference in Berlin last month, assessed
the effect of an over-70 screening program in the Netherlands
on breast cancer-related deaths.
SENIOR
SCREENING
The authors of the first study, conducted at M D Anderson
Cancer Center in Houston, Texas, found that in those
who went for regular screening, breast cancers were
diagnosed at an earlier disease stage. In step with
this observation, breast-cancer specific five-year survival
jumped from 82% for women who didn't get any screening
done to 94% for those who had regular mammograms. Patients
who underwent screening at irregular intervals had a
five-year survival of 88%. Since the most benefit was
seen for regular use of mammography, the authors conclude
that their results support screening at intervals of
one to two years in this age group.
This is the first time that such
recommendations can be made on the basis of hard data.
Indeed, the current lack of explicit guidelines is a
direct result of the fact that most trials and studies
to date have excluded women older than 69. "The new
evidence should help physicians to be more assertive
when recommending screening to women over 70," says
Dr Warner. "If a woman is healthy at age 70, she has
a life expectancy of 15 years, so it's well worth doing
the screening."
In addition to the cancer stats,
the research yielded a surprising result regarding breast
cancer-unrelated survival in women over the age of 80:
the five-year survival rate was 59% for those who didn't
go for regular mammograms, and 80% for women who did.
The authors were unable to separate this effect from
the trend seen in breast cancer-specific survival, so
they concede there may be a bias for healthier patients
to undergo more regular screening.
The Dutch study appears to confirm
what the American researchers found. It showed that
breast-cancer related deaths fell by 30% in the Netherlands
after the upper age limit for screening was extended
to 75 there. The new guidelines took effect in 1998,
and researchers from the Erasmus Medical Center in Rotterdam
decided to look at data from 2003 onwards to see whether
there was an observable effect. They found that deaths
from breast cancer were steadily declining in women
aged 75-79, i.e. the bracket where improvements in survival
would be expected. Between 1986 and 1997, roughly 166
per 100,000 women in this age group died of breast cancer
per year. In 2006, that number was down to 117.
Until guidelines catch up with
the research, Canadian physicians will just have to
play it by ear. "In terms of comorbidity, the treating
physician has to decide on an individual basis what
kind of screening is appropriate," says Dr Warner. "If
a woman isn't able to undergo mammography, you can still
do a clinical breast exam."
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