"If I had a forum to talk to women who have had breast cancer and also have sisters, I would tell them it's important to get their sisters involved [in the Sister Study] and encourage them. It's important to do this to find out all we can." —Wanda Willis

As Tina Hall goes about her everyday business, she takes pride in knowing she's doing her part to fight breast cancer. She's not a doctor or a politician or a philanthropist. She's one of thousands of women across the US and Puerto Rico taking part in the Sister Study, a 10-year clinical trial aimed at finding the causes of breast cancer.

Tina and the other participants have never had breast cancer themselves, but are sisters of women who have. Tina's sister, Wanda Willis, was diagnosed with breast cancer in 2003, at age 41. Their mother and grandmother also had the disease and died from its complications before age 50.

"The only thing we knew about cancer in our family was that it was a death sentence," says Tina, a special-education teacher in Winston-Salem, North Carolina.

All that changed with Wanda's diagnosis, however. Although her treatment was difficult -- surgery, 6 months of chemotherapy, and 6 weeks of daily radiation treatment -- Wanda has bounced back and feels better than ever. She walks 6 miles several days a week, has just finished her master's degree, and is starting a therapeutic massage organization for cancer patients called Touch Therapy.

"I feel great," she says. "My hair has come back. I feel stronger and more youthful than before. It's wonderful."

It was Wanda who asked Tina to join the Sister Study. She learned of the project at a meeting of the Sisters Network, Inc., a national organization for African-American breast cancer survivors, and immediately realized its importance.

Tina did, too. "Because it was my way to support her, I didn't have any reservations about it," she says of signing up.

The study focuses on genetic and environmental factors that might be linked to breast cancer. Women who take part must answer detailed questions about their diet, jobs, hobbies, and other things. They also give samples of blood, urine, toenail clippings, and household dust.

Giving samples was easy, Tina says. Remembering details about her past -- what she ate as a teenager, what products she used -- was harder.

Now that she's completed those parts, though, all she has to do is a periodic telephone interview with researchers. The study does not require participants to take any medications or undergo other physical exams, and they are not asked to change their diets or daily habits.

So far the study has enrolled 27,000 women, but researchers need another 23,000 to sign up. They're especially interested in recruiting ethnic and racial minorities -- African Americans, Hispanics/Latinas, Native Americans, Asian/Pacific Islanders -- because less is known about breast cancer in these groups than in white women.

That point is important to Wanda Willis.

"If there's a clue linked to what we do culturally, then we need to be represented in the study as well," she says.

Breast cancer survivors of all races need to encourage their sisters to join the study, she adds, even if cancer is a difficult subject to broach.

"Nobody wants to talk about it but it needs to be talked about," she says. "We can't just sweep it under the rug once we feel like we're well."

For her part, Tina discusses her participation in the study every chance she gets and distributes informational materials when possible. She hopes the study helps researchers find a cure for breast cancer -- or even better, a way to prevent the disease.