Dr Joel Brind and others have postulated that if ALL the women who had had abortions
had been counted in the Melbye study, the study would have found a very high incidence of breast cancer among peri menopausal and post
menopausal, aborted women. Dr Melbye admitted in the conclusion of the
study that the data may not be accurate because many women having abortions
before computerization were not included in the cohort. One wonders how Dr
Melbye could triumphantly tell the media that the matter was settled (no
link) when he knew most of the women at menopausal age had not been
counted?? Roy Spencer, former NASA climatologist explains that
Scientists are human and if they don't come up with eye catching headlines,
they may not get funding. You can hear Dr Brind talk about the
abortion/breast cancer link in the video below. (his article follows)
Article by Dr. Joel Brind
The Culture of Life Foundation -
Published in the Jan. 9 issue of the prestigious New England Journal of
Medicine2, (NEJM) the most recent study on abortion and breast cancer was hyped
most brazenly by it’s own lead author, Dr Mads Melbye of the Statens Serum
Institut in Copenhagen. "I think this settles it. Definitely--there is no
increased risk of breast cancer for the average woman who has had an abortion",
Melbye told The Wall Street Journal 3.
Headline news stories trumpeted these conclusions worldwide, and lead editorials
from the NEJM4 itself to The New York Times 5 echoed the reassuring counsel that
women "need not worry about the risk of breast cancer" when considering abortion
4.
What the Melbye study claimed to find was an overall breast cancer risk increase
of exactly 0.0% among Danish women who had had at least one abortion. Actually,
a few other studies (five6-10 out of twenty-nine, to be exact) had also found no
tendency toward increased risk.
Even if the Melbye study were entirely valid, it would still be outrageous to
claim that one single study, on a population of women from another continent,
could somehow prove that women from the U.S. and elsewhere were not put at
increased breast cancer risk by choosing abortion. After all, ten studies11-20
out of eleven on American women have shown increased risk, eight of them13-20
statistically significant on their own! This fact alone belies the political
agenda behind claims that the "issue should now be settled" 21, that "the notion
that abortions cause breast cancer (has been) largely disproved" 5.
Such claims, however, were reportedly based on two aspects of the Melbye study
which were supposed to put it head and shoulders above the rest, namely: 1) It
covers an extremely large population, i.e., all 1.5 Danish women born from April
1, 1935 to April 1, 1978, and 2) It relies entirely on prospective (see
glossary, page 7) computerized records, which are considered more accurate than
data based on women’s own recollections, on which most other studies were based.
But this study’s flaws are many and ultimately, fatal.
The errors in the Melbye study may be grouped into three categories, as detailed
below:
1) The inappropriate selection of computerized data from Danish birth, abortion
and breast cancer registries
a) The use of birth records back to 1935 meant that women in the study were as
old as 38 when the computerized abortion registry began, so records of abortions
among them are largely missing. This is reflected in the extremely atypical age
distribution of the patients in the study who had any abortions. As shown in
Figure 1, the majority of these patients are on record as having had their
abortions over the age of 35, whereas the average abortion client in Denmark is
only 2722 (in the US, she is only about 2223). The acknowledgement of this
source of error by Melbye et al. epitomizes understatement: "we might have
obtained and incomplete history of induced abortions for some of the oldest
women in the cohort." In fact, since abortion was legalized in Denmark in 1939
(although Melbye et al. misrepresent this as well: "In 1973, the legal right to
an induced abortion through 12 weeks’ gestation was established for women with
residence in Denmark."), the published record of legal abortions from 1940 to
197322 reveals that 60,000 women in the Melbye study cohort listed as not having
had any abortions, actually did have abortions! That means Melbye et al., who
listed 281,000 women as having abortions, misclassified more than one of every
six women in the study cohort who had an abortion. Importantly, these are also
the oldest members of the cohort, which makes them the majority of the women who
have gotten breast cancer.
b) The inclusion of women born as recently as 1978 inflates the population size
studied by over 350,000 subjects. That is the number of women born between 1968
and 197822, who were therefore under 25 at the termination of the study in 1992.
Almost no one gets breast cancer that young. The published Danish records show
that these young women account for a grand total of only 8 cases of breast
cancer25-28, which amount to less that one tenth of one percent of the 10,246
cases of breast cancer in the study. In contrast, these young women account for
over 40,00022, or 11% of the 371,000 induced abortions reported in the study.
c) The inclusion of women who got breast cancer between 1968 and 1973 is
patently ridiculous: Of course every one of these over 300 patients25 is listed
as having no abortions, since abortions before Oct. 1, 1973 are not included in
the study! This error, of course, serves to lower, artificially, the calculated
relative risk.
2) Invalid statistical adjustment of the raw data
The consequence of selecting such an inappropriately large segment of the Danish
population is the need to adjust substantially the calculated value of relative
risk to account for the large age differences between the average woman who had
an abortion and the average woman who got breast cancer. This adjustment tends
to raise the relative risk estimate. Interestingly, the raw relative risk (more
precisely, the rate ratio) is not shown in the paper, although enough data are
shown to calculate it (1.44, or a 44% increased breast cancer risk). As a round
figure, the real, adjusted breast cancer risk increase attributable to abortion
for this study population would seem to be around 100%! (Indeed, an earlier
study on part of this population29 reported an almost 200% risk increase with
abortion among childless women.) Yet somehow, Melbye et al. end up with an
adjusted relative risk estimate of exactly 0.0%!
What Melbye et al. did was to adjust the data for birth cohort. A birth cohort
refers to a population of people born during the same time period, and it
differs from the adjustment for age. Age adjustment corrects for the fact that
breast cancer risk increases with a woman’s age. Therefore, one must adjust the
relative risk estimate upward if one’s study compares women with cancer who are,
on average, older than the cancer-free women in the study. The birth cohort
adjustment is supposed to correct for the fact that breast cancer risk differs
for women who are the same age when they get breast cancer, but who were born at
different times. For example, the breast cancer incidence among 50-year-old
women born in 1940 was higher than that for 50-year-old women born in 1930,
since the incidence of breast cancer has been steadily on the rise for most of
this century for women of any given age.
All this seems quite reasonable except for one extremely crucial fact: The
reason why breast cancer has been on the rise for most of this century is
unknown. If abortion is one of the reasons, adjusting for this birth cohort
effect, as Melbye et al. did, necessarily eliminates the effect of the very
factor under study (abortion) and virtually guarantees the null result they
obtained! In fact, the pattern of breast cancer risk with time25-29 in women in
Denmark, is seen to move in striking parallel to the pattern of induced abortion
exposure22. Figure 2 shows the close correlation of age-adjusted breast cancer
risk and frequency of induced abortion, examining the data on all Danish women
in 5-year (the standard interval used) birth cohort groupings.
3) Mischaracterization of their own findings and of other published research in
the field.
a)Even on the paper’s face, the "Conclusions" section of the abstract of Melbye
et al. is noteworthy for its brevity: "Induced abortions have no overall effect
on the risk of breast cancer." Yet even with the paper’s eggregious flaws, it
still evidenced a statistically significant trend of increased breast cancer
risk with increasing gestational age at abortion. Thus, as their data table
shows, they found a 12% risk elevation at 11-12 weeks (late first trimester)
rising to an 89% risk increase for abortions later than 18 weeks. This didn’t
show up in their "overall" relative risk figure, because most abortions in
Denmark (as in the US) are done somewhat earlier (7-10 weeks) in the first
trimester, and their effect on breast cancer risk was statistically eliminated
(see section 2 above).
b) Melbye et al. also make no mention in the abstract or the discussion of the
fact that they found a 29% increased breast cancer risk among women who had an
abortion as a teenager. The reason the authors were able to avoid mentioning
this statistic is the fact that it was not statistically significant. The reason
it was not statistically significant is the small number of women in this
category in their study, due to the recent inception (1973) of the computerized
abortion registry they used.
c) The authors disparage and dismiss the findings of the worldwide literature
compiled in our 1996 "Comprehensive review and meta-analysis"1 with the blanket
statement: "it is not unreasonable to assume that many of them (the 23 worldwide
studies we compiled) were inherently biased, making the pooled conclusions
biased as well." (See the "Brief guide to epidemiological study design and
interpretation", page 7 of this issue.) Two important points should be made
here: i) The potential problem of bias in case-control control studies, is, as
Melbye et al. point out, that it would, if it exists, result in the
"differential misclassification" of women who had abortions as not having had
abortions. The irony here is that the very study of Melbye et al. takes the
proverbial cake for misclassification by orders of magnitude, considering their
misclassification of 60,000 women (see 1a above)! ii). The overall average 30%
risk increase attributable to induced abortion which we reported in our
meta-analysis, and which Melbye et al. take exception to, is virtually the same
statistic they obtained for women who had abortions as teenagers (see 3b above).
d) Melbye et al. misrepresent their findings as essentially confirming the
findings of other researchers who investigated the ABC link using prospective,
computerized data: "This result is very much in line with the results of
previous ... cohort studies". To back this statement up, they cite four studies,
three of which30-32 concern only (or mostly) spontaneous abortion (miscarriage),
and are therefore entirely irrelevant. (See article in this issue for why
miscarriages don’t usually increase breast cancer risk.) They also conveniently
ignore the fact that one of the studies showing significantly increased risk
(90%) also used prospective computerized data14.
It is of course outrageous that the Melbye study, is being used to spread the
claim that the ABC link does not exist. This is not good news for women, who are
still actively being kept in the dark by the very agencies who should warn them
about avoidable cancer risks. In this regard, Dr. Patricia Hartge, author of the
NEJM editorial4 which accompanied the Melbye study, is only the most recent
National Cancer Institute researcher disparaging the link. However I find it
encouraging that the ABC debate is finally out in the open. I have already
published a brief rebuttal in The Wall Street Journal33, and coauthored another
which is in press in the NEJM34. The fact that Melbye et al. did such a bad job
will only hasten the day when the ABC link will be common knowledge. -jb-
Dr. Joel Brind, Ph.D.of Baruch College in New York City, is one of the leading
researchers in the area of Abortion-Breast Cancer link. He is also on the
Advisory Board of the Life Research & Communications Institute.
NOTE: Joel Brind's personal website is down at this time and the
footnotes have been lost. I am searching for these at the present time.
Apologies (no one seems to think footnotes are important - I got this from a
reprint on another site).