Cherie Miller is only 26 and has never had cancer. And yet some time before her 28th birthday she plans to undergo a double mastectomy.

What the Santa Rosa woman does have is a genetic mutation that vastly increases the likelihood that she will get breast cancer at a young age.

Miller's mother was just a baby when her 28-year-old mother was diagnosed with the disease. As a tiny pre-schooler, Miller watched her mother suffer through sickness and treatments, only to die at the age of 31. Miller was just 5.

For Miller, the thought of losing her breasts, however difficult, is not as traumatic as the potential alternatives.

"I would never want to go through the experience of radiation and chemotherapy, because that was what was really difficult to watch with my mom and why I want to avoid that so much," Miller said. "I don't want to go through all the hell to try and fix it, and then to die anyway."

Miller tested positive for a breast-cancer (BRCA) gene mutation, which accounts for 5 to 10 percent of all breast cancers and one in seven ovarian cancers, according to the National Institutes of Health.

The BRCA1 and BRCA2 genes, when normal, help prevent uncontrolled cell growth. But when there is a mutation — both men and women can carry the gene and can pass it on — a woman faces not only a higher risk of breast cancer, but also a significantly higher risk for ovarian cancer as well as other types of cancer, depending on which gene mutation she has. Men with the mutation also have a higher risk of breast and other cancers.

The BRCA gene mutation is the most common cause of hereditary breast cancer and a significant cause in younger women. It is only one, however, of a number of risk factors that women should be aware of. Knowing what those factors are, experts say, can reduce a woman's chance of getting the disease or increase her chances of surviving it if she does, by catching the cancer in the early stages when it's most treatable.

"The most significant risk for breast cancer is being older and being female," said Paula Kelleher, a nurse practitioner with the Kaiser Santa Rosa Breast Care Center. "In fact, three-fourths of all cases are over the age of 50."

There is no absolute predictor or magic bullet to prevent a disease that kills 40,000 women a year. Even women with a BRCA gene mutation may never get cancer.

Yet, there are some lifestyle choices women can make to decrease their risk, like maintaining a healthy body weight, getting regular exercise, limiting alcohol consumption and eating a good diet rich in fruits and vegetables, poultry, fish and low-fat dairy products.

There are several other gene mutations that have been connected to certain cancers and can be tested for, said Dr. Amy Shaw, director of the Cancer Survivorship and Prevention Program for the Redwood Regional Medical Center in Santa Rosa.

Beyond that there are other risk factors women may not be able to control but would be wise to be aware of. It appears that the more menstrual periods a woman experiences in a lifetime, the more vulnerable she is to breast cancer. That means that early onset of menstruation, late onset of menopause and not having children may increase one's odds of developing breast cancer. Conversely, breast feeding, which can delay menstruation, may provide some protection.

For women who may have a family history, however, risk awareness is particularly crucial. And yet, many women may not know that significant relatives, like grandmothers or aunts, also had breast cancer. Or they also may not think to look at their father's side of the family.

That was the case with Lori Loomis, a Petaluma woman who underwent treatment for breast cancer for the first time in 1998. At the time, a young cousin from Germany was visiting and mentioned that her mother, who was the same age as Loomis, also was battling breast cancer.

Loomis didn't connect the dots, however, until her dad mentioned a few years later that the cousin had died.

"I said, &‘Oh my gosh. I'm glad it's not my future.' He said, &‘Actually, all the women on my side of the family in Germany have died of breast cancer as far as I know.'"

Loomis, an in-home energy and telecommunications systems broker, was moved to action. She underwent genetic counseling. And while she hasn't taken the step to confirm through genetic testing that she has the BRCA gene mutation, given her extensive family history and her own history with the disease, her doctors presume she does. She agreed to have her ovaries and uterus removed as a precaution.

Lydia Zipp of Petaluma survived stage-four ovarian cancer when she was 34 and yet made no connection between that and any family history. But then 10 years ago, she read in the book "Gilda's Disease" by actor Gene Wilder, whose wife, comedian Gilda Radner, died of ovarian cancer, that the disease was often spoken of historically as "stomach cancer." She realized her own grandmother died of what was called "stomach cancer."

When she started digging deeper and talking to family members, she found out "there was so much breast and ovarian cancer in our family history I didn't know about," all on her father's side.

Armed with that information, she met with a genetic counselor and went through genetic testing, a process that helps women sort out their risks and options. While some high-risk women, like Miller, choose to undergo prophylactic mastectomy and or removal of their ovaries and fallopian tubes (the odds of ovarian cancer increase after age 35) Zipp opted instead to take the drug tamoxifen and undergo increased surveillance. That means clinical breast exams twice a year and yearly mammograms and MRIs.

For every woman, the choice may be different, although never easy. But information may bring more peace of mind.

"I wasn't at the point where I wanted to make that decision about prophylactic mastectomy," said Zipp, who created and heads the Women's Cancer Awareness Support Group of Petaluma. "What I advocate is for people to talk to a genetic counselor so they can make an informed decision about whether or not they should and want to be tested."

Shaw said only 5 percent of women meet the criteria for a recommendation to get genetic testing, a blood test covered by most major health insurance plans including Medicaid and Medicare for women with a history of breast cancer.

The information can have important ripple effects throughout a family, from daughters and sons to sisters and distant cousins, either signaling they may also be at risk or giving them the peace of mind that they are not.