A study was presented at
the 2008 San Antonio Breast Cancer Symposium (SABCS) about
the risk of lymphedema when flying. A news release about
that study came out in the on-line newsletter,
MedPageToday.
According to the news release, the
study found that women who've had breast cancer surgery
"need not worry" about developing lymphedema when flying.
But, that isn't what the
researchers said in their report. The results and
conclusions in their SABCS meeting abstract (Abstract #1119)
are different from what the news release says. Here's a
link to a page with a search engine that can be used to type
in the abstract number and access the abstract of the study:
http://www.abstracts2view.com/sabcs/sessionindex.php
The study involved 75 women who had
recovered from breast cancer surgery and were flying to
Queensland, Australia, to participate in a dragon boat
regatta. The researchers used "bioimpedance" to measure
extracellular fluid in the arms of the women before and
after the airplane flights.
One problem with the study is that
bioimpedance was the only method the researchers used to see
if the women had developed lymphedema. Some lymphedema
researchers and clinicians think bioimpedance might not be
sensitive enough to detect lymphedema until it reaches a
severe form (Stage III). So, swelling that was less severe
might not have been detected in this study.
According to the news release in
MedPage Today, 5% of the women in
the study did develop a "clinically significant"
increase in arm fluid, as judged by bioimpedance. Five
percent seems like enough of a risk to warrant taking
precautions when flying. What is odd is that the
researchers reported a different number in their
abstract--not 5%--for the prevalence of "clinically
significant" arm fluid. They said 15 of the 75 women
developed a "clinically significant" increase; and 15 of 75
is 20%, not 5%. Twenty percent is considerable risk. Most
women would probably think a risk of 20% was worth "worrying
about," and worth taking precautions.
But not all the women in the study
were at equal risk of developing lymphedema. Of the 75
women, 12 took fairly short flights to Queensland from other
locations in Australia. Only one of those 12 women had a
"clinically significant" accumulation of arm fluid. The
other 63 women in the study flew all the way to Australia
from Canada, which was a much longer flight--a "long haul"
flight, according to the researchers. Among the 63 women
who took the trans-oceanic flights, 14 had a "clinically
significant" increase in arm fluid. So, the women on the
longer flights had a 14/63 = 22% chance of
developing a "clinically significant" increase in arm
fluid. That number would likely attract most women's
attention and cause them concern.
According to the researchers, 8 of
the 15 women who had a "clinically significant" increase in
arm fluid had enough of an increase for it to be diagnostic
of lymphedema (i.e., they actually developed lymphedema).
All 8 of those women were on the flights from Canada. That
means 8/63 = 12.7% of the women who took the trans-oceanic
flights developed bona fide lymphedema in association with
their flights. The news release said all but 2 of those
women had been diagnosed with lymphedema previously. That
statement implies that lymphedema triggered by flying is
somehow less important if it is a recurrence than if it is a
new case. In contrast to that statement in the news
release, the number of new cases reported in the abstract
was much higher. The researchers said in their abstract
that 6 of the 8 women diagnosed with bona fide lymphedema in
association with the flight had not had arm swelling prior
to the flight--this was a new diagnosis of lymphedema for
them.
Finally, the news release failed to
emphasize an important point: The women in this study were
traveling to Australia to participate in a dragon boat
regatta. According to the researchers, 94% of the women in
the study had "trained at a moderate to vigorous
intensity for the regatta." We can probably assume
they were in pretty good shape--their upper-body
conditioning was likely much better than that of most women
after breast cancer treatment. Several studies have shown
that a supervised exercise program involving upper-body
strength training can reduce the risk of lymphedema after
breast cancer surgery. Wouldn't that mean the women in this
study were at lower risk of developing lymphedema in the
first place? So, why would the news release mislead their
readers by generalizing the findings to all women?
The first sentence in the news
release says, "Women who've had breast cancer surgery
need not worry that pressure changes in an airplane cabin
will bring on lymphedema, researchers found." But
that's very different from what the researchers concluded in
their abstract. Here's what the abstract said: "For
the majority of women who undertake moderate to vigorous
upper limb exercise, airplane travel did not have a
significant impact on extracellular fluid ratio."
Those two statements mean very
different things. The discrepancies in representation of
the results of this study are troubling, and should be
clarified for the benefit of all women who have been treated
for breast cancer and are facing the risk of lymphedema.
