A majority of high-risk women in a University of Michigan study declined to take a drug found to be successful in reducing a woman’s chance of developing breast cancer, a new study shows.

The study examined the interest in the drug Tamoxifen and tailored information to women who participated in the study. The majority of the women who say they would opt not to take the drug said the potential side effects outweigh its preventative benefits.

Women in the study - who had no history of breast cancer, but had been determined to have an increased risk of the disease - were tested on information about the drug itself and were later asked if they would take it. 

After providing the information, researchers found at least 63 percent of participants could correctly answer 5 out of 6 questions about the risks and benefits of Tamoxifen. Fewer than 30 percent said they would ask their doctor or otherwise seek more information about it. Only 6 percent said they'd take Tamoxifen.

Results of the study appear online in the journal Breast Cancer Research and Treatment.

Angela Fagerlin, an U-M associate professor in internal medicine and a VA Ann Arbor Healthcare System research investigator, was lead author of the study. Much of her time is spent examining patient decision-making when it comes to tough medical choices, such as the course of treatment for a prostate cancer near the end of life or the use of living wills.

“With this study, we were trying to find out good methods for communicating risk and benefit information to patients trying to make an important medical decision," Fagerlin said. "The second part of the study was meant to understand a woman's interest in taking a breast cancer prevention drug when she understood her exact breast cancer risk and had information tailored to her own history.”

Fagerlin spoke with AnnArbor.com in a telephone interview about the study.

Q: What does Tamoxifen do?
A: Tamoxifen can reduce a woman's 5-year risk of breast cancer by 50 percent and can also reduce (her) risk of bone fractures. But (in rare cases) it can also increase their risk of endometrial cancer, as well as blood clots, which could lead to stroke or deep vein thrombosis. It can increase a patient’s chance of cataracts and hormonal effects such as hot flashes and sexual problems, including a reduction in libido. It’s also important to note - that is a 50 percent reduction in risk, but (the woman's) absolute risk is generally between 2 to 3 percent so we’re only talking about 1 percent here.

Q: How well did women understand the information you were giving them about this drug?
A: People got it. On average, people answered 4.3 of the (6) questions correctly, 63 percent answered 5 of the 6 questions we asked them correctly. The knowledge of the women was quite high. What was more surprising is the women who had the higher knowledge who were more likely to say they would not want to take Tamoxifen while those who seemed to have less understanding were more likely to say they would take it.

Q: Why did so many women say they weren’t interested in this drug?
A: It wasn't bad decision making … the women said the prevention was not worth the risk of the drug. They also didn’t like the idea of taking a drug every day for the next five years.

Q: Why is this important?
A: We’re trying to understand better what would a breast cancer prevention drug look like in order for a woman to want to start taking it and what risk benefit trade-offs would a drug have to have to have for a woman to take it. We’re trying too look at how patient make medical decisions and how to we improve that process. I think what we found here is women were making informed decision about taking this drug, they weighed their risk and benefits to take this drug, and did not find a compelling case. I think this shows us if we take the time to give women the tailored information about risk and benefits, they can make informed decisions.

Tina Reed covers health and the environment for AnnArbor.com. You can reach her at tinareed@annarbor.com, call her at 734-623-2535 or find her on Twitter @TreedinAA.