Breast cancer study attracts attention at convention here

Protein made during pregnancy shows promise in tests on mice

November 04, 2005|By DENNIS O'BRIEN | DENNIS O'BRIEN,SUN REPORTER

The pain of childbirth comes with an often forgotten benefit: Pregnancy reduces the mother's risk of breast cancer.

Now, researchers who gathered in Baltimore this week say they may have found a way to mimic nature and reduce the risk for all women.

So far, they have only experimented in mice, often a dead end for cancer therapies when the results can't be repeated in humans. But other scientists are particularly hopeful that this research will pan out.

Here's how it works: When a woman is pregnant, the fetus produces a protein that shows up in the mother's blood around the 12th week of gestation. Known as alpha feto-protein (AFP), the substance reduces the mother's chance of developing breast cancer later in life.

Researchers say that a mother reduces her risk of breast cancer each time she becomes pregnant. The younger she is the first time, the greater the benefit. Having twins or triplets increases the beneficial effect.

The phenomenon has been documented for years. Researchers in Texas found in 1998 that a woman who becomes pregnant before the age of 20 has about half the risk of breast cancer as a woman whose first pregnancy occurs at 26 or later.

The findings are the basis of a cancer therapy being studied by a team of researchers who discussed preliminary findings at the Frontiers in Cancer Prevention Research conference at the Baltimore Convention Center.

Scientists at Albany Medical College in New York created a peptide - a chain of amino acids - with the same chemical characteristics as AFP and gave it to thousands of mice that had been implanted with breast cancer cells. The team found that their peptide, which they call AFPep, stopped the growth of the cancer cells and reduced the number of tumors in the mice by 23 percent.

When AFPep was combined with tamoxifen - a drug now used to treat breast cancer - it reduced tumors by 77 percent.

"This is a new proposal and a brand new way of looking at breast cancer treatment," said Thomas T. Andersen, a biochemist and cancer researcher at the medical college.

Tamoxifen has been used for nearly 20 years to treat breast cancer. As a cancer therapy, it works to counteract the effects of estrogen, which is believed to promote the growth of breast cancer cells.

Although experts say that tamoxifen's benefits far outweigh its risks, studies have linked it to side effects that include blood clots, eye problems and uterine cancer.

Andersen said AFPep could reduce tamoxifen's side effects and noted that it's effective when given orally or by injection - a major advantage. He is looking for a pharmaceutical firm to sponsor human clinical trials, an expensive process required before drugs are approved for marketing and one that takes at least three to five years.

Breast cancer causes about 48,000 deaths each year in the United States. With 180,000 new cases diagnosed each year, it's the second most common cancer among women, after skin cancer.

Andersen said that if the trials are successful, AFPep could be used as both a breast cancer therapy and a drug that prevents breast cancer in healthy women.

"Pragmatically, I don't care if it's used for treatment or prevention, if we somehow can prevent cancer in the long run, that's what matters," Anderson said.

Other scientists say the study shows AFPep is worth additional research.

"Those are fascinating results," said Donald Coffey, a cancer expert and director of research at the Brady Urological Research Lab at the Johns Hopkins School of Medicine.

Aspirin's benefits

In preliminary findings from another study, researchers said that women who took an average of four or more low-dose aspirin (commonly known as baby aspirin) each week over 10 years reduced their risk of breast cancer by 34 percent.

Women who took the same number of regular-strength aspirin over that 10-year period showed a 50 percent increased risk of breast cancer.

Many doctors tell patients to take either a regular-strength aspirin or a low-dose aspirin each day for cardiovascular health, but researcher Anne Ready of the Fred Hutchinson Cancer Research center in Seattle said it was too soon to recommend the low-dose.

Hutchinson scientists analyzed the aspirin-taking habits of 35,368 women between the ages of 50 and 76. All completed a 54-page questionnaire between 2000 and 2002 as part of a larger, more comprehensive health study. Of that group, 363 women had developed breast cancer as of December 2003, Ready said.

She said that the number of cancer cases is still too small to draw conclusions and that there may be other reasons some women developed breast cancer and others did not.

"Is this a real effect, or is there something about these women that take baby aspirin - something about their lifestyle - that seems to be conferring this added benefit?" Ready asked.

Dr. Ernest Hawk, a researcher and administrator at the National Cancer Institute, said that aspirin should be the focus of a human clinical trial to determine who should take it and who should avoid it.

Numerous observational studies - in which the health habits of large groups of people are surveyed and analyzed - have documented aspirin's ability to boost cardiovascular health and prevent some colon cancers.

Such studies also have shown that aspirin causes gastrointestinal bleeding in 1 percent of the population, said Hawk, who is director of NCI's office of centers, training and resources.

But a full-scale clinical trial - in which some people are given aspirin and their health is compared with a group given a placebo - would be the most comprehensive way to determine whether aspirin's benefits outweigh its risks, Hawk said.

"To me, it's the only way you can answer these kinds of questions," he said.

dennis.obrien@baltsun.com

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