A new study published in the Asian Pacific Journal of Cancer Prevention in February reported a very statistically significant increased risk of breast cancer for women with previous abortions as opposed to women who have never had one.
The study, consisting of 1,351 women and led by researcher Ai-Ren Jiang, reported a statistically significant 1.52-fold elevation in risk for women with induced abortions and a “significant dose-response relationship between (the risk) for breast cancer and number of induced abortions,” meaning the risk climbed with a higher number of previous abortions.
For premenopausal women who have had abortions, the numbers were relatively small, and the observed 16% risk elevation was not statistically significant. However, for those with three or more abortions, the risk climbed to a statistically significant 1.55-fold elevation.
“The results have revealed that induced abortion was related to increased risk of breast caner. Premenopausal women who had ≥3 times of induced abortion were at increased crude odds ratio (OR) (2.41, 95%CI: 1.09-5.42) and adjusted-OR (1.55, 95%CI: 1.15-5.68),” they wrote. “Postmenopausal women with a previous induced abortion were at increased crude OR (2.04, 95%CI: 1.48-2.81) and adjusted-OR (1.82, 95%CI: 1.30-2.54), and there was a significant increase trend in OR with number of induced abortions (p for trend: 0.0001).”
Karen Malec, of the Coalition on Abortion/Breast Cancer, who noted the study, said that postmenopausal women with a history of abortion experienced a statistically significant 1.82-fold elevation in risk, compared to those with no abortion history.
“Risk climbed with number of IAs (induced abortions) from a statistically significant 1.79-fold increased risk for one IA and a statistically significant 1.85-fold elevation for two IAs, to a non-statistically significant 2.14-fold elevated risk for three or more IAs,” Malec said.
“Professor Joel Brind (Baruch College, City University of New York) advised the Coalition on Abortion/Breast Cancer that earlier Chinese studies underestimated the breast cancer risk of IAs,” Malec said. “A one-child-per-couple policy is in force, and most women have abortions after first full term pregnancy. (First full-term pregnancy reduces risk by maturing 85% of the mother’s cancer-susceptible breast lobules into permanently cancer-resistant lobules.)”
Brind said it “tends to suppress the relative risk values, which makes the Jiang numbers all the more credible – underestimates if anything. Also, a place like China is good to measure the dose effect of abortion, and the statistics are strong enough to show a highly significant trend, which strengthens a causal inference.”
Malec also noted that a Chinese study in 1995 by L. Bu and colleagues, including Janet Daling of the Fred Hutchinson Cancer Research Center, reported a statistically significant 4.5-fold elevated risk among women with previous induced abortions who developed breast cancer at or before age 35, compared to older women (who experienced a statistically significant 2.5-fold elevated risk).
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“Four of seven Chinese studies report statistically significant risk increases for women with IAs,” Malec concluded. “Fifty-three of sixty-nine epidemiological studies dating from 1957 report risk elevations for women with previous IAs. Biological and experimental research supports an abortion-breast cancer link.”
As other studies have shown, this new one from China indicated miscarriages do not elevate a woman’s breast cancer risk.
“Overall, spontaneous abortion did not significantly alter the risk of breast cancer, but postmenopausal women who had history of spontaneous abortion were at increased odds ratio,” they wrote. “These results suggested that relationship between breast cancer and abortions may depend on menopausal status and induced abortion played an important role in the development of breast cancer in Jiangsu’ women of China.
Citation: Jiang AR, Gao CM, Ding JH, Li SP, Liu YT, Cao HX, Wu JZ, Tang JH, Qian Y, Tajima K. Abortions and breast cancer risk in premenopausal and postmenopausal women in Jiangsu Province of China. Asian Pacific J Cancer Prev 2012;13:33-35. Available at: http://www.apjcpcontrol.org/page/popup_paper_file_view.php?pno=MzMtMzUgMTIuMiZrY29kZT0yNzAxJmZubz0w&pgubun=i