Abortion and Breast Cancer Risk
A committee in the Massachusetts state legislature is now considering a bill that would require doctors in that state to tell women considering an abortion that the procedure may increase their risk of breast cancer. Similar legislation is currently being considered in 16 other states.
Needless to say, the issue is extremely volatile. Pro-life groups vigorously support the bills; abortion rights organizations strongly oppose them. And the debate is all the murkier because the research linking abortion and breast cancer risk is inconclusive at best.
Both the National Cancer Institute (NCI) and the Royal College of Obstetricians & Gynaecologists (RCOG) in the U.K. have recently weighed in on the debate.
After an extensive review of studies regarding a possible link between abortion and breast cancer, the NCI has concluded that the evidence of a direct relationship between breast cancer and either induced or spontaneous abortion is "inconsistent." The agency noted that some studies have indicated small elevations in risk, while others have not shown any risk.
In a summary statement, it cited a 1997 report published in The New England Journal of Medicine that found no increase in breast cancer incidence among Danish women who had undergone abortions. Importantly, that study relied on data from the Danish Health Registry which was collected before the diagnosis of breast cancer, thus eliminating any recall or reporting bias that may have skewed other conclusions on the subject.
Most early studies on abortion and breast cancer were retrospective; that is, they relied on women's personal reports of their reproductive history, making them subject to recall bias. Women with breast cancer were more likely to accurately report sensitive reproduction issues, such as having had an abortion, than women without breast cancer. The NCI statement noted that this type of reporting bias could make abortion appear to be more common among women with breast cancer, possibly leading to the false conclusion that abortion increases the risk of breast cancer.
For example, an earlier study published in the Journal of the National Cancer Institute found a significant increase in risk for breast cancer after an induced abortion. However, the authors themselves, Rookus and van Leeuwen of The Netherlands Cancer Institute, suggested that this figure may have been influenced by inaccurate recall associated with the underreporting of abortion by healthy control subjects in the religiously conservative southeastern region of The Netherlands. In the more liberal western regions of the country, the association between abortion and breast cancer was statistically insignificant. Rookus and van Leeuwen concluded that their study "does not support an appreciably increased risk for breast cancer after an induced abortion."
In response to this and other studies, the National Cancer Institute released a blanket press statement: "Taken together, the inconsistencies and scarcity of existing research do not permit scientific conclusions."
The Royal College of Obstetricians and Gynaecologists in the U.K. issued a similar statement. "The RCOG wishes to reassure women who have had an abortion or who have breast cancer that the research evidence on this question to date is inconclusive.
"The association found in some studies has not been found in others of equal quality," the College emphasized, noting that few if any studies have shown "any significant association between abortion and breast cancer."
SOURCES:
National Cancer Institute (http://www.nci.nih.gov)
The Royal College of Obstetricians and Gynaecologists (http://www.rcog.org.uk)
Additional references cited by the National Cancer Institute:
Brinton LA, Hoover R, Fraumeni JF. Reproductive factors in the aetiology of breast cancer. Br J Cancer 1983;47:757-762.
Daling JR, Malone KE, Voigt LF, et al. Risk of breast cancer among young women: Relationship to induced abortion. J Natl Cancer Inst 1994;86:1584-1592.
Gammon MD, Bertin JE, Terry MB. Abortion and the risk of breast cancer: Is there a believable association? JAMA 1996;4:275:321-322.
Kelsey JL, Gammon MD, John EM. Reproductive factors and breast cancer. Epidemiol Rev 1993;15:36-47.
Kelsey JL. Breast cancer epidemiology: Summary and future directions. Epidemiol Rev 1993;15:256-263.
Lindefors-Harris BM, Eklund G, Adami HO, et al. Response bias in a case-control study: Analysis utilizing comparative data concerning legal abortions from two independent Swedish studies. Am J Epidemiol 1991;134:1003-1008.
Melbye M, Wohlfahrt M, Olsen JH, et al. Induced abortion and the risk of breast cancer. N Engl J of Med 1997;336:81-85.
Parazzini F, La Vecchia C, Negri E. Spontaneous and induced abortions and risk of breast cancer. Int J Cancer 1991;48:816-820.
Remennick LI. Induced abortion as cancer risk factor: A review of the epidemiological evidence. J Epidemiol Community Health 1990;44:259-264.
Rookus, MA, van Leeuwen, FE. Induced abortion and risk for breast cancer: Reporting (recall) bias in a Dutch case-control study. J Natl Cancer Inst 1996;88:1759-64.
Rosenberg L, Palmer JR, Kaufman DW, et al. Breast cancer in relation to the occurrence and the time of the induced and spontaneous abortion. Am J Epidemiol 1988;127:981-989.
Rosenberg L. Induced abortion and breast cancer: More scientific data are needed. J Natl Cancer Inst 1994;86:1569-1570.
Tavani A, Vecchia C, Franceshi S, et al. Abortion and breast cancer risk. Int J Cancer 1996;65:401-405.
[Table of Contents] [Archived Issues / Search] [The Breast Center]