The following Melbye/Danish report, was supposed to disprove the Abortion Breast Cancer link. Dr. Joel Brind points out its fatal flaws.

The New England Journal of Medicine recently published a Danish abortion study by Melbye et al. The lead author told the Wall Street Journal: "I think this settles it definitely. There is no overall increased risk of breast cancer for the average woman who has an abortion." In an accompanying editorial an official of the National Cancer Institute stated, "The clear central finding is that there is no overall risk." The pro-abortion media picked up this description of the study and headlined it across this nation and the world.

It was exactly what they wanted to hear, and they swallowed these comments without any attempt to evaluate whether or not they were valid. Headline news stories trumpeted these conclusions worldwide, and lead editorials from the NEJM itself to The New York Times echoed the reassuring counsel that women, "need not worry about the risk of breast cancer" when considering abortion.

We now have an exhaustive review of this research article by the man who is probably the most qualified judge of the validity of such studies in the world, Dr. Joel Brind:

"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 (five^6-10 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 out of eleven studies on American women have shown increased risk, eight of them, statistically significant on their own! This fact alone belies the political agenda behind claims that the "issue should now be settled", that "the notion that abortions cause breast cancer (has been) largely disproved.

"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 April1, 1978.

2) It relies entirely on prospective 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.

"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 27 (in the US, she is only about 22 ).

The acknowledgement of this source of error by Melbye et al. epitomizes understatement: 'we might have obtained an 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 1973.

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 1978, 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 cancer, 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 40,000, 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 patients 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 population 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 therelative 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!

Continued

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