The two drugs also kept precancerous growths from becoming cancerous, says researcher Sang-Hyuk Chung, PhD, a research associate at the McArdle Laboratory for Cancer Research at the University of Wisconsin School of Medicine and Public Health in Madison.
"If it's translatable to humans, then it may open up another treatment possibility," Chung tells WebMD. His study is published in PNAS Early Edition.
But experts who reviewed the research for WebMD say it must be viewed as preliminary. Chung agrees, saying, "It will take years to get results from potential clinical trials."
An estimated 11,270 new cases of invasive cervical cancer are expected in the U.S. this year, according to the American Cancer Society; about 4,070 women will die from the disease. Cervical cancer treatment options include surgery, chemotherapy, and radiation, depending on the stage at which it is detected.
Drug Treatment for Cervical Cancer: Study Details
Chung and Paul F. Lambert, PhD, also at the University of Wisconsin, tested the drugs on mice genetically engineered to carry human papillomavirus (HPV) 16, a strain that is strongly associated with cervical cancer.
In the U.S., genital HPV is the most common sexually transmitted infection, according to the CDC. New HPV vaccines can prevent some infections but can't eliminate infections already present or precancerous growths. There are many different HPV strains.
Although many women become infected with HPV, few develop cervical cancer, as the virus often clears on its own. Since not all HPV-infected women get cervical cancer, Chung and others have long suspected another factor is in play. They decided to focus on estrogen, a hormone to which the cervix and other female organs are responsive.
It's known that long-term use of birth control pills, as well as multiple pregnancies, increase the risk of cervical cancer in HPV-infected women, Chung writes.
In their mouse model, estrogen is required for cervical or vaginal cancer to develop, according to Chung.
So Chung and Lambert gave the mice either Faslodex, used to treat certain breast cancers, or Evista, used to treat osteoporosis and to reduce the risk of breast cancer in some women. One group of animals with cervical cancer was untreated.
The drugs prevent estrogen from working in the cervical cells, according to the researchers.
After a month, the researchers looked at the results. Over 90% of those treated with either Faslodex or Evista did not have cancer, Chung says. The drugs also were effective in eliminating precancerous growths.
"At this point I cannot say whether one [drug] is better than the other," he says.
Chung says the drugs may one day provide another cervical cancer treatment option.
The real value of the research may prove to be showing experts a more precise model of how cervical cancer develops, says Margaret Madeleine, PhD, an assistant member of the Fred Hutchinson Cancer Research Center and research assistant professor of epidemiology at the University of Washington School of Public Health in Seattle, who reviewed the findings for WebMD.
''There may be more interest in it as a model of how cervical cancer might develop in the presence of birth control pills or [multiple pregnancies], both known risk factors [in HPV-positive women]," she says.
Ernest Han, MD, PhD, gynecologic oncologist and assistant professor at the City of Hope Comprehensive Cancer Center in Duarte, Calif., calls the research finding an interesting concept.
Overall, he says, ''our detection [of cervical cancer] is pretty good.'' Pap tests look for cervical cell changes caused by HPV so the cancer can be detected early. However, "treatment for advanced cancer and for patients who have recurrences is poor," he says.
The study, however, has limitations, Han says. It was small. It would be ''a leap" to say this may soon be a treatment for cervical cancer. ''We'd have to see more definitive studies."