Michels study showing no link between abortion and breast cancer IS VERY FLAWED

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A new study by Karin Michels and her colleagues on the link between abortion and breast cancer is seriously flawed, said the Coalition on Abortion/Breast Cancer. They found almost no increase in risk - a 1.01 hazard ratio for women who had one or more abortions. [1]

"We call on journalists to challenge Michels et al. to conduct a proper study that allows sufficient follow-up time between exposure to abortion and the development of breast cancer," said Karen Malec, president of the coalition. "Ask the researchers whether the person who smokes cigarettes today will develop lung cancer next month or whether it takes years to develop the disease."

Michels et al. collected abortion and breast cancer data during all ten years of the study. To do the study properly, they should include only abortions procured up to 1993 and then follow their study subjects for ten years. At least four other studies [2,3,4,5] in recent years have been criticized for the same reason. [6,7]

The Journal of American Physicians and Surgeons published a review of 10 prospective studies that are being used to deny an abortion-cancer link. [6] The study concluded that the 10 studies are significantly flawed and cannot be used to invalidate the larger body of research showing a link. No scientist has attempted to shoot down these conclusions.

"This isn't the first time that Harvard Nurses Study researchers [8] have produced the wrong epidemiological results," said Joel Brind, president of the Breast Cancer Prevention Institute. "They were wrong about combined hormone replacement therapy {HRT) reducing the risk of heart attack and stroke [9], and they're wrong about abortion."

The U.S. National Cancer Institute (NCI) funded the new study, Michels et al. 2007. Ten years ago, NCI expert Patricia Hartge editorialized against the abortion-cancer link in the New England Journal of Medicine [10] when the Danish study [5] was published showing no overall increase in risk. Even though the Danish study found a statistically significant 89% increase in risk for women who have abortions after 18 weeks gestation, Hartge concluded, "In short, a woman need not worry about breast cancer when facing the difficult decision of whether to terminate a pregnancy."

"So why has the NCI continued to spend millions of dollars to fund studies on the abortion-cancer link?" asked Malec. "Clearly, its scientists must either suspect a link or know that it exists."

In their paper, Michels et al. criticized the Danish study [5] for "possibly introducing nondifferential misclassification" - an allegation that Brind made ten years ago. [11] Brind criticized the Danish study for misclassifying tens of thousands of women who'd had abortions as not having had them. The U.S. Department of Defense helped fund the Danish study.

Michels et al. suggested that the findings from earlier retrospective studies reporting an increased risk of breast cancer for women who had an abortion may have been due to a hypothetical problem called "report bias." If true, this would mean that the results from the retrospective studies were artificial. Those who argue that report bias exists say that the only reason why scientists found an increased breast cancer risk among women who've had abortions is because more sick women accurately report their abortion histories than do healthy women.

The problem is that there are no scientists today who claim to have found credible evidence of the existence of report bias. Moreover, even Karin Michels' earlier research did not find evidence of its existence.

Michels was a co-author in the study, Lipworth et al. 1995. [12] That study was published about five months after the study, Daling et al. 1994. [13] Both studies reported the same risk increase for women who have abortions - a 51% increase in risk in the former study and a 50% increase in the latter study.

Lipworth et al. tested for report bias by reviewing Greek literature. They concluded, "even before legalization, induced abortions were practiced in Greece with widespread social acceptance. This can be interpreted as indicating that healthy women then in Greece report reliably their history of induced abortion." Consequently, Lipworth et al. did not find evidence of report bias.

Nevertheless, Michels misled Dr. Lawrence Altman, epidemiologist reporter for the New York Times about the existence of report bias. Lipworth et al. was submitted for publication on October 20, 1994, but only one week later on October 27, 1994 Altman interviewed Michels about the study, Daling et al. She told him "that is a flaw in the design because women who have breast cancer are more likely to disclose an abortion than women who did not develop breast cancer." [14]

In their latest paper, Michels and her colleagues speculated that abortion might protect women from breast cancer. They wrote:

"Because levels of human chorionic gonadotropin rise in the early stages of human pregnancy, an incomplete pregnancy of short duration might impart the benefits of a full-term pregnancy and thus reduce the risk of breast cancer."

Brind, however, scoffed at this idea. He said, "That kind of speculation is what has been disproved by 50 years of epidemiology."

The study, Michels et al. 2007, focused on the debated breast cancer risk - whether abortion leaves women with an increased number of cancer-vulnerable breast lobules. It did not focus on the recognized breast cancer risk - the loss of the protective effect of a full term pregnancy.

"Even the NCI agrees that increased childbearing, starting at an early age, protects women from breast cancer," said Malec. "Legislators have a moral obligation to require abortion providers to inform expectant mothers that if they have an abortion, their breast cancer risk will be higher than it would be if they have a baby. That's settled science."

References:

1. Michels K, Xue Fei, Colditz G., Willett W. Induced and Spontaneous Abortion and Incidence of Breast Cancer Among Young Women. Arch Int Med 167:814-820.

2. Palmer J, Wise L, Adams-Campbell LL, Rosenberg L. A prospective study of induced abortion and breast cancer in African-American women. Cancer Causes and Control 2004;15:105-111.

3. Reeves G , Kan S, Key T, Tjønneland A, Olsen A, et al. Breast cancer risk in relation to abortion: Results from the EPIC study. International Journal of Cancer 2006;119;7: 1741 - 1745.

4. Tang NC, Weiss NS, Malone KE. Induced abortion in relation to breast cancer among parous women: A birth certificate registry study. Epidemiology 2000;11:177-80.

5. Melbye M, Wohlfahrt J, Olson JH, Frisch M, Westergaard T, Helweg-Larsen K, Andersen PK. Induced abortion and the risk of breast cancer. N Engl J Med 1997;336:81-85.

6. Brind J. Induced abortion as an independent risk factor for breast cancer: A critical review of recent studies based on prospective data. J Am Phys Surg Vol. 10, No. 4 (Winter 2005) 105-110. Available at:
<http://www.jpands.org/vol10no4/brind.pdf>.

7. Brind J. Letter. Int J Cancer 2007; in press.

8. Stampfer M, Colditz G, Willett W, et al. N Engl J Med. 1991 Sep 12;325(11):756-62.

9. Writing group for the Women's Health Initiative Investigators. Risks and benefits of estrogen plus progestin in healthy postmenopausal women. JAMA 2002;288:321-33.

10. Patricia Hartge. Editorial: Abortion, Breast Cancer, and Epidemiology. New England Journal of Medicine 1997;336:127-128.

11. Brind J, Chinchilli VM. Letter. Induced abortion and the risk of breast cancer. N Engl J Med 1997;336:1834-1835.

12. Lipworth L, Katsouyanni K, Ekborn A, Michels KB, Trichopoulos D. Abortion and the risk of breast cancer: a case-control study in Greece. Int J Cancer 1995;61:181-184.

13. Daling JR, Malone DE, Voigt LF, White E, Weiss NS. Risk of breast cancer among young women: relationship to induced abortion. J Natl Cancer Inst 1994;86:1584-1592.

14. Altman L. New study links abortions and increase in breast cancer risk. The New York Times, October 27, 1994. A-24.

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