As noted above, in terms of the ABC link, there are really no new findings as such; rather, a repeat of the modest but significant prior findings of the studies from the 1990’s, i.e. those two studies - Daling et al. 1994 and Daling et al. 1996 - had reported ORs for induced abortion and breast cancer of between 1.2 and 1.5. Hence, the reported OR in the present study of 1.4 was not really new. But what was striking was the way in which the finding of a significant ABC link was characterized. Specifically, abortion appears in the data table which lists the associations found for “known and suspected risk factors”. In the text, the effect of the significant risk factors, including induced abortion, were described as “consistent with the effects observed in previous studies on younger women.” Hence, this paper provides clear support for the existence of the ABC link.But what is really new here is that one of the coauthors of this study is one Louise A. Brinton of the NCI. Importantly, Brinton was the chief organizer for the 2003 NCI (U.S. National Cancer Institute) “workshop” on “early reproductive events and breast cancer”, a panel which reported that the lack of an ABC link had been “established”. In other words, since 2003, the NCI has firmly maintained the position that there is no ABC link; that the studies which had reported such a link were deemed unreliable. However, two of these prior studies were the very studies by the Daling group (of which one Brinton also was a co-author). [2,3] Now, in 2009, Brinton is on record reiterating findings of the ABC link and reporting them as “consistent” with earlier studies that found induced abortion to be a risk factor.
Can it not therefore be argued that the NCI is backing off its denial of the ABC link? This is big news, to be sure, but no one has challenged the NCI with it, yet.
My understanding from the Mayo Clinic study a few years back is that the stronger breast cancer association with oral contraceptives is found in women who use OCPs without having previously carried a pregnancy to term. This would fit with elective abortion as a risk factor, especially if the abortion were also prior to first term pregnancy, which is quite frequently the case. The original safety studies done on OCPs inadvertently used a skewed population, not representative of today’s users. The “pill” was primarily tested on married women who didn’t want MORE children, not those delaying childbearing or preventing pregnancy altogether - hence studies did not pick up on breast cancer risk to women without a prior term pregnancy.
There is nothing in what you posted that backs up the claim in the story. If you’re familiar with scientific research publication, you should know that published abstracts note any conclusions reached by the researchers. What they often don’t include are random bits of statistical artifacts that did not have statistical significance and/or that the study was not designed to evaluate. The claim that this study “found” a 40% increase in a fairly common type of breast cancer *causatively* related to abortion is absurd (nor did it even find any significant association). Even the leading proponents of this junk science theory have never claimed finding any effect remotely in that ballpark.
There are lot of known risk factors for breast cancer, and many of them are statistically more common in women in women who also have abortions. Delayed and/or absent childbirth, alcohol consumption, and early onset of menstruation come to mind. Mild associations between abortion and breast cancer are thus easy to find, but no unbiased, empirically valid study has ever found a causative relationship, or even more than a very mild associative relationship.