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Oflc@ fl[ CBt1Cer Communications owou+o : Bathesaa I Nationai Institutes of Health October 26, 1994 Linda Anderson NCI Press Office (301) 496-6641 Abortion and Possible Risk for Breast Cancer: Analysis and Inconsistencies • A study reported in the Nov. 2 issue of the Journal of thc Natroncl Cancar brstitute (INCI) * on induced abortion and risk for breast cancer discusses whether an association exists, but the findings are not conclusive. Further research is needed to interpret the results. The rcsearch was independently conducted by Janet Daling, P1r.D., Fred Hutchinson Cancer Rese..rch Center, University of Washington, Seattle, and colleagues. The study suggests that women age 45 or younger who have had induced abortions have a relative risk of 1.5 (50 percent increse3 risk) for breast cancer compared to women who had bee.~ pregnant but never had an induced abortion. ~ In cpide.rnio3ogic resrarch, relative risks of Ieu than 2 are considered small and are usually difficult to interpret. Such increases may be due to chance, statistical bias, or effe,cff of confounding factors that are sometimes not evident. In an editorial accompanying the study, Lynn Rosenberg, Sc.D., Boston University School of Medicine, points out that a 'differenc= in risk of 50 percent (relative risk of 1.5) is smzil In epidemioIogie teerms (human ~ population studies) and sevezeiy challenges our ability to distinguish whether it reflects =se ~ ~ and effca or whether it simply reflects bias. tt ~ ~ «p.

Rosenberg notes that "the overall results as well as the parcicuiars are far from Conciusive, and it is difficult to see how they will be informative to the public." Daling and colleagues did not find a consistent pattern of increasing or decre asino risk. associated with age at abortion, as would be exaected by many scientists. (Risk was greater for women who had their first induced abortion before age 18 (relative risk of 2.5) and for women who were 30 years of age or older (relative risk of 2.1).) Furthermore, the risk did not vary by number of abortions, whether abortion preceded or followed a full-term pregnancy, or by length of time to diagnosis of breast cancer. One key point is that women aged 45 or younger who had miscarriages were not found to be at increased risk for breast Taken together, the inconsistencies and scarcity of existin; research do not permit scientific conclusions. In the Daling study, the researchers analyzed data on 845 white women who were diagnosed with invasive or in situ breast cancer from 1983 to 1990 and 961 control subjects. All the women were born after 1944. Data were collected on reproductive history, family history of breast and other cancers, and lifestyle and other factors. The study population was from three counties in Washington State. Only white women were included in the study b• ctse of the small minority population m ' ' this area. The research-rs also found that risk for breast cancer was more enhanced for women having an induced abortion prior to age 18 if their pregnancy was interrupted during the 9-to-24•week period of gestation. However, this futding was based on small numbers. (more)

Siudies published in the JNC1 are pe-mr-reviewed by scier.dsts and represent the vieivs of the authors. Papers published in the journal do not-necessaiily reflect the views he:d by NCI or any other component of the federal government. wThe paper is titled "Risk of breast caaces among young women: Re3ationship to induced abortion." The authors are Janet R. Daling, Kathian E. Malone, Lynda F. Voigt, Emily White, and Noel S. Weiss, of the Fred Hutchinson Cancer Research Center, Unitiersity of Washington, Seattie. "Press statements can be downloaded from CornpuServe: The documents are io.:atui in the "SciNews-MedNews library" which is in the Journaiism forum (Ga IFaRZJM). This document is av;zilable through the National Canc=r Institute's CancerFax and CancerNet services, and in the News Section of the NC's PDQ database. To get the document from ~ CancErraz, dial (301) 402-5874 from the handset on your fa.r machine and follow the recorded instructions to receive the contents list. Individuals who have access to the Internet may access the document on CancerNet, through an electronic mml seniice or via the NIKH gopher. To get the CancerNet contents iist from the e-mail servicx, send an e-mail message that says 'help' in the body of the message to cancernetOicicb.nc.i.nib.gov. To get the documents from Canceri~'es via tr.e NIH gopher, point your gopher client to gopher.nih.gov ind look for CancerNet under "Health and Clinic3l Liformation.' To get the document from NCI's PDQ database, access PDQ News on the National Li'brary of Medirane's MEDLARS systern or consuIt a medicai Iibrasian for assistance. 0