A geographic portion of southern Sonoma County has been identified as one of two Northern California regions with higher than average rates of invasive breast cancer, researchers said this week.
The portion is defined by a single 2010 census tract that includes the southern edge of the city of Sonoma, though it is primarily rural.
The findings are detailed in a report released Tuesday by the Oakland-based Public Health Institute's California Breast Cancer Mapping Project. The report, which covers the period from 2000 to 2008, pinpoints four previously unidentified regions where cases of invasive breast cancer have been significantly higher than the state average.
These four "areas of concern" include two regions in Southern California, one in the South Bay and one that encompasses the northern Bay Area. The latter region -- which includes the Sonoma County census tract -- circles San Pablo Bay and includes portions of Marin, Napa, Solano and Contra Costa and Alameda counties.
Breast cancer is the most common cancer among women in California. Each year an average of 26,3000 women are diagnosed with breast cancer and about 4,175 die from it.
Unlike county-level surveillance data, the mapping project examined breast cancer rates within and across county boundaries by looking at data from the California Cancer Registry against census tracts.
The report does not explain why these four regions showed breast cancer rates that were higher than the state average. But authors of the report said they hoped the data would serve as an important epidemiological tool for county and state health officials.
"We found that the specific communities most impacted by breast cancer can fall within or across counties. By identifying these communities we can more efficiently and effectively direct resources to them," said Dr. Eric Roberts, principal investigator of the mapping project, in a statement.
Dr. Dennis McDonald, the former director of the Sutter Women's Health Center in Santa Rosa, said he had always heard that certain regions of Northern California have a higher incidence of breast cancer.
McDonald, who was recently transferred to Sacramento to head up Sutter Health's regional women's imaging program, said breast cancer diagnosis rates detected at the Sutter Women's Health Center in Santa Rosa were higher than the national average.