Past Study Indicates Abortion Increases Risk of Breast Cancer - Brief Article - Statistical Data Included

Nutrition Health Review, Wntr, 2001

Having an induced abortion may increase a woman's risk for breast cancer later in life by nearly one third, according to a review and statistical analysis of 23 studies of women with breast cancer, which appeared in the October 1996 Journal of Epidemiology and Community Health, published by the British Medical Association.

"The evidence is overwhelming," said Vernon Chinchilli, Ph.D., co-author and associate director of the Center for Biostatistics and Epidemiology at Penn State University's Milton S. Hershey Medical Center, where the studies were conducted. Eighteen of 23 studies indicated an increased risk in women who had an induced abortion, he said. The meta-analysis covers 23 separate studies with data on 25,967 women with breast cancer and 34,977 control patients without cancer.

"Our study documents a clear and significant link in worldwide published epidemiological research dating back to the first study in Japan in 1957," said principal investigator Joel Brind, Ph.D., professor of Endocrinology at Baruch College in New York City. "Yet most women are still in the dark: only three states require that women considering abortion be warned about breast cancer." The three states are Louisiana, Mississippi, and Montana.

Brind had researched connections between sex hormones and human disease for nearly 25 years. He said that pregnancies ending in early miscarriage--often called "spontaneous abortions"--do not expose women to high levels of estrogen. "Excess exposure to estrogen is involved in most known breast cancer risk factors," said Brind. "But in most pregnancies that end in miscarriage, estrogen levels never get off the ground, so breast cancer risk is not increased."

Abortion may result in an increased risk in young, childless women in two ways, said Joan Summy-Long, Ph.D., professor of Pharmacology at Hershey. "They lose the protection of a full-term pregnancy in addition to gaining the 30 per cent risk increase from the abortion," she said.

"In normal pregnancies that do go to term, hormones secreted near the end of pregnancy modify the growth and vulnerability of breast cells, resulting in lower risk for women who have children," she said. Summy-Long is a neuroendocrinologist who studies hormonal regulation of milk secretion.

Induced abortion already accounts for about 5,000 cases of breast cancer in the United States every year, according to the four authors of the study. The number of cases is expected to rise to over 25,000 a year by the mid-21st century, as the initial group of women exposed to legal induced abortion in the 1970s continues to age.

Accounting for the increased risk, the researchers estimate that the 800,000 first-time abortions performed annually would thus generate roughly 25,000 excess cases of breast cancer each year as the first group of women exposed to legal abortion advances in age. Given the margin of error, the researchers predicted that excess cases of breast cancer would be between 9,000 and 40,000 a year because of the impact of induced abortion.

These data clearly raise the issue of risk when an abortion is induced by a pill such as RU-486 rather than by the usual surgical means, said co-author Walter B. Servers, Ph.D., Professor of Pharmacology at Hershey.

Noting that "abortion is the most common elective surgical procedure currently performed in the United States," the researchers also note that other elective health risks such as smoking require thousands of exposures for measurable increases in cancer incidence to occur.

By comparison, one induced abortion is enough to increase breast cancer risk. The authors state, "... the induced abortion patient's risk of breast cancer later in life is measurably increased after a single exposure."

Chinchilli said that five of the six new studies published since their meta-analysis support the same correlation between induced abortion and breast cancer. "The numbers always go in the same direction, regardless of the variance," he said.

"The incidence of breast cancer has increased over the last 25 years," said Servers. "The number of abortions is one major variable that has changed during that time."