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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."