Women suffering from the most common source of female infertility in the United States -- a condition known as polycystic ovary syndrome (PCOS) -- may have an improved chance to become pregnant thanks to a drug developed to combat breast cancer, doctors say.
In PCOS, which affects around 5 percent to 10 percent of all women, cysts form on the ovaries, often accompanied by irregular periods.
A study published in The New England Journal of Medicine describes a treatment for PCOS based on the use of the breast cancer drug letrozole, commonly prescribed for postmenopausal women with cancers that are impacted by estrogen.
Letrozole causes the ovaries to increase production of the hormone.
In the study trial, funded by the National Institutes of Health, about 28 percent of women taking letrozole successfully achieved a live birth, compared to 19 percent taking the drug clomiphene, prescribed for years to help PCOS women become pregnant.
The drugs were given to study participants during five menstrual cycles, and the dosage was increased for each cycle.
Letrozole provided better rates of ovulation, conception and births, the researchers say.
"We found a simple and comparatively safe and vastly more effective treatment for [polycystic ovary syndrome]," says lead researcher Dr. Richard Legro, a Penn State professor of gynecology and obstetrics.
One drawback to the tradition treatment with clomiphene, which is intended to stimulate ovulation, has been a high incidence of multiple births.
Women receiving letrozole experienced fewer multiple pregnancies when compared with those receiving clomiphene, the researchers say, around 3 percent as against 7 percent.
"Clomiphene may be trumped," Legro says. "To see a 40 percent improvement in birth rate is a huge difference."
Both drugs have apparent but manageable side effects, the researchers found; clomiphene users reported hot flashes, while some women reported fatigue and dizziness wit letrozole.
The encouraging findings will likely lead to more doctors prescribing letrozole as an infertility treatment, along with continued use of the older drug, experts say.
Letrozole, a generic drug, is relatively inexpensive, matching the costs of the long-established clomiphene of about $56 for 30 pills.
"This is an affordable form of infertility treatment," Legro says.
The question of birth defects arises with any use of fertility drugs, but birth defects were rare and rates were similar for both clomiphene and letrozole, comparable to rates in women who conceive without treatment, he says.