Article About the Sister Study Featured in Marin Independent Journal of California
CAN SISTERS PROVIDE BREAST CANCER CLUE?
- Richard Halstead
Novato resident Joan Rentsch is one of more than 24,000 women across the country
who have volunteered so far to participate in a 10-year study of the sisters
of breast cancer victims.
The purpose of the study is to learn more about the role that environmental factors play in causing breast cancer, said study project investigator Dr. Dale Sandler, an epidemiologist with the National Institute of Environmental Health Studies based in Durham, N.C.
Rentsch's sister Virginia was diagnosed with breast cancer in 2000. The cancer was removed, and so far, there has been no recurrence.
Previous studies have focused on women who have been diagnosed with breast cancer already. It is difficult to judge the effect of environmental factors retrospectively, Sandler said.
"If you want to measure something in people's blood, or you want to ask about their exposures, you have to worry that the effect of having cancer may alter what you measure, or may have changed women's lifestyles or behaviors," Sandler said.
To eliminate this possible bias, researchers wanted to study women before they were diagnosed with breast cancer. There was a problem, however. Despite how common breast cancer may seem, it is a relatively rare disease.
Joan
Rentsch of Novato is participating in a new national breast cancer study
of the incidence of the disease among sisters. Rentsch holds a photo of
her sisters (from left) Barbara McCarthy, Virginia Candee and Catherine
Candee. Viginia Candee was diagnosed with cancer in 2000. (IJ photo/Robert
Tong)
"We would need to study a really large population of women, or follow the woman for more years than I have left in my research career," Sandler said.
The sisters of breast cancer victims provide a partial solution to this problem. That is because, due to shared genes and lifestyle, sisters of women with breast cancer have, on average, twice the risk of developing breast cancer.
"So by studying sisters, we could do a prospective study with half the number of women," Sandler said. The goal is to find 50,000 women to participate in the study.
Rentsch learned about the study through the American Cancer Society in San Rafael, where she works one day a week.
"I thought, 'Great, something I can do,'" said Rentsch, who worked for a county health department in New Jersey as an educator before moving to California two years ago.
Rentsch said one of the reasons she was motivated to work for the American Cancer Society was the concern about breast cancer in Marin. Breast cancer rates in Marin and San Francisco are about 6 percent higher than rates in other Bay Area counties and 15 percent higher than rates in California overall.
Delaying childbirth has been identified as one possible cause, along with obesity, alcohol consumption and hormone replacement therapy.
Rentsch said she has been impressed by the study's attention to detail. Participants are asked questions about their lifestyle, medical history, jobs and other environmental factors. They complete questionnaires about diet and family cancer history. And they provide samples of blood, urine, toenails and even house dust.
"They asked me a lot of questions about where I grew up and whether we were near any high-tension power lines or a hazardous waste site," Rentsch said.
Rentsch has four sisters. The oldest, Barbara, was born in 1942. Joan was born in 1944. Virginia was born in 1947 and Catherine was born in 1950. There was no prior history of breast cancer in their family.
Even though both Barbara and Joan have used hormone replacement therapy, which has been identified by other studies as a risk factor for breast cancer, it was Virginia who was diagnosed with breast cancer.
"There are a lot of unanswered questions about who gets breast cancer and why," Rentsch said. "So if this study can help, I'm very glad to participate."