• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

Study Links Antibiotics and Breast Cancer

Posted on: Monday, 16 February 2004, 06:00 CST

A study suggests antibiotics might increase the risk of developing breast cancer, but researchers said the data should not stop women from taking the medication.

Women who took the most antibiotics - who had more than 25 prescriptions, or who took the drugs for at least 501 days - faced double the risk of developing breast cancer over an average of about 17 years, compared with women who didn't use the drugs, the study showed.

The authors said more research is needed because it could have been the diseases women used antibiotics to treat - rather than the drugs themselves - that increased breast cancer risk.

Also, since antibiotics are widely used to treat a variety of common infections caused by bacteria, including strep throat, some pneumonias and many gastrointestinal infections, it may be that women who never took the drugs were unusually healthy and therefore unusually resistant to cancer, the researchers said.

"It's very premature for people to stop taking antibiotics when they're needed," said lead author Christine Velicer, a researcher at Group Health Cooperative, a large nonprofit health plan in western Washington. "Antibiotics have a substantial public health benefit."

The results appear in Wednesday's Journal of the American Medical Association and were released Monday.

The study involved 2,266 women 20 and older who developed invasive breast cancer and who were compared with 7,953 women who did not get breast cancer.

An increased breast cancer risk was found with increasing use of antibiotics, with the greatest increased risk in women who took the drugs for at least 501 days. Even women who had up to 25 prescriptions over about 17 years faced an increased risk - about 1.5 times higher than nonusers.

An increased breast cancer risk was found for all types of antibiotics, including penicillins.

A few theories might explain how antibiotics would lead to breast cancer, Velicer said. The medications' effects on intestinal bacteria could change the body's immune system or how the body metabolizes foods that protect against cancer, she said.

An JAMA editorial says the theorized link is potentially worrisome, since antibiotics are so commonly used - sometimes unnecessarily for conditions in which they are ineffective, including colds and other viruses.

But more research is needed before the drugs can be implicated, said editorial authors Dr. Roberta Ness and Jane Cauley of the University of Pittsburgh.

---

On the Net:

JAMA: http://jama.ama-assn.org

More News in this Category