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Research by the Public Health Institute Identifies New Communities Within California with Elevated Breast Cancer Rates

November 27, 2012

Study pinpoints geographic “areas of concern” not previously identified

Oakland, CA – New research by the Public Health Institute’s (PHI) California Breast Cancer Mapping Project (CBCMP) has pinpointed four previously unidentified areas of California that have invasive breast cancer rates substantially higher than the state average. The four “areas of concern” encompass sections of Ventura, Los Angeles, Riverside and Orange counties, as well as parts of the north and south Bay Area. The CBCMP released these findings today in a full report available here.

As opposed to traditional breast cancer surveillance, which relies on aggregate county-level data, the CBCMP developed and implemented a protocol to map breast cancer rates within and across county boundaries by looking at data (obtained from the California Cancer Registry, or CCR) by census tract. This identified the four areas of concern, or groups of census tracts that showed invasive breast cancer rates 10-20 percent higher than the state average between 2000-2008. (2008 was the most recent data available when the study began.) Since these areas span sections of multiple counties, they had never been identified by traditional county-level surveillance as having elevated breast cancer rates.

“Breast cancer doesn’t know geographic boundaries and this study shows that mapping breast cancer rates by census tract is a useful and important supplement to county-level surveillance, which is still essential,” said Eric Roberts, MD, PhD, principal investigator of the CBCMP. “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.”  

Detailed maps of the four areas of concern are available in the CBCMP report. They include:

  • An area that includes neighboring portions of Ventura and Los Angeles counties. Previous analyses examining these two counties separately had not yielded this information.
  • An area that includes the southern portion of Orange County and a small portion of western Riverside County showed higher breast cancer rates than the state average. However, Orange County as a whole had previously shown only slight elevations with intermittent statistical significance; Riverside County had shown a significantly lower breast cancer rate than the state average.
  • Portions of the northern San Francisco Bay Area, including not only Marin (as was previously known) but also parts of Sonoma, Napa, Solano and Contra Costa counties have a higher breast cancer risk.
  • Portions of the southern San Francisco Bay Area, including communities in San Mateo County, northern Santa Clara County and southern Alameda County have a consistently elevated risk of breast cancer.

Based on these findings, public agencies and other service providers may consider targeting outreach efforts in these areas and strengthening screening, treatment and support services.

The CBCMP maps highlight new areas of concern, but are not designed to determine the causes of breast cancer rates or detect specific environmental triggers. Although scientists are concerned about the role that environmental pollutants play in breast cancer, research shows that cancer often does not develop until decades after these exposures take place. The CBCMP maps, based on where women live at the time that they are diagnosed, do not reveal where they lived previously, or which pollutants they may have been exposed to.

 “The California Cancer Registry and its regional registries have monitored cancer incidence in California since 1988, usually by county or large regions. By using CCR data to map the entire state with this mapping protocol, the CBCMP is adding to ongoing surveillance activities in an important way,” said Dr. Dee West, executive director of the Cancer Registry of Greater California. “The findings from this report should be studied in more detail to benefit the breast cancer community – from patient to provider to researcher.”   

The CBCMP report also analyzed sociodemographic factors of women with breast cancer in the four areas of concern and found that, in general, the findings reflected known sociodemographic patterns in breast cancer risk for the state, including elevated risk for white women. However, women diagnosed in the Ventura/Los Angeles area of concern had less private insurance compared to the other areas of concern and the state overall.

Public agencies, breast cancer advocates, and communities can use the CBCMP’s mapping protocol by census tract and mapping results going forward to identify communities most impacted by breast cancer, explore resource needs and opportunities, and suggest avenues for future research. Developed by the CBCMP’s advisory group, which was composed of diverse stakeholders representing the breast cancer community, the mapping protocol maintains widely accepted standards of scientific rigor and protects patient confidentiality. The advisory group emphasizes the importance of conducting health tracking to protect the public’s health and recommends that state agencies involved in health surveillance consider using this or a similar protocol on a routine basis. 

“The CBCMP mapping protocol is a very useful tool to enhance surveillance of breast cancer, and possibly other cancers, at the local level,” continued Roberts. “We look forward to exploring how it can be more widely utilized by public agencies and other stakeholders.”

Browse video, print and radio coverage of the study.

For more information contact:
Ann Whidden, MPH, PHI senior communications manager, at 415.425.5157 or awhidden@phi.org.

About the California Breast Cancer Mapping Project
The CBCMP, a project of PHI, was funded by the California Breast Cancer Research Program of the University of California. The CBCMP was guided by staff from the PHI and an advisory group representing breast cancer advocates, clinicians, and public health agencies. For more information, visit www.californiabreastcancermapping.org.

About the Public Health Institute
The Public Health Institute, an independent nonprofit organization, is dedicated to promoting health, well-being and quality of life for people throughout California, across the nation and around the world. PHI's primary methods for achieving these goals include: sharing evidence developed through quality research and evaluation; conducting public policy and advocacy; providing training and technical assistance; and promoting successful prevention strategies to policymakers, communities and individuals. For more information, visit www.phi.org.