Breast cancer was the most common type of new cancer diagnosed in women in the United States in 2015. It was the second most deadly cancer after lung, accounting for an estimated 40,290 deaths. The lifetime risk for an American woman of developing breast cancer is 12.3 percent. Largely due to increases in screening and improvements in treatment, mortality rates have declined overall by 36 percent since their peak in 1989. Yet, the gains have not been realized uniformly across all regions or all racial/ethnic groups in the U.S.

In this study, Dr. Paulo Pinheiro, an associate professor in UNLV’s School of Community Health Sciences, and students Karen Callahan, Nevena Cvijetic, and Rachel E. Kelly collaborated with the Nevada Central Cancer Registry and the Sylvester Comprehensive Cancer Center of the University of Miami Miller School of Medicine to produce a telling publication about the breast cancer rate disparities among women in Nevada. The results were published in the article Worse Breast Cancer Outcomes for Southern Nevadans, Filipina and Black Women in the Springer Journal of Immigrant and Minority Health.

Methodology

Registry data were obtained for women diagnosed with breast cancer between 2003 and 2010. For the first time in Nevada, the researchers used enhanced registry data by making linkages with the National Death Index as well as the Social Security Administration Masterfile. This improved the accuracy of survival data by minimizing the number of missing deaths. Population-based, five-year, cause-specific overall survival was calculated for the entire state. Survival was stratified by race/ethnicity. Stage-specific survival was stratified by Nevada region.

The Results

Of the 11,111 cases of breast cancer identified from 2003 to 2010 in the Nevada Central Cancer Registry:

• Most cases were from Southern Nevada (68 percent) among women with private insurance (45 percent).
• Almost one-third of all cases occurred in women under age 55.
• The overall five-year survival rate in Nevada was 84.4 percent, significantly lower than the U.S. proportion of 89.2 percent.
• Survival in Northwestern Nevada (88.2 percent) was significantly higher than in Southern Nevada (83.0 percent). The rural survival estimate was also low (84.3 percent).
• Women from Southern Nevada with breast cancer had a 16 percent higher risk of death than women from the state’s second highest population center, Northwestern Nevada.
• By race/ethnicity, survival was highest for Asian (non-Filipina) women, at 89.5 percent.
• Filipinas and blacks showed a disadvantage in survival compared to all other racial/ethnic groups analyzed, at 76.6 percent and 76.0 percent, respectively.
• Stage at diagnosis was the most influential risk factor.

Implications

Research found that black women are likely to suffer from lower survival rates because they are more likely to have aggressive tumors and they are typically diagnosed at later stages. In addition, the researchers found differences in mammography screening, higher proportions of obesity, delays in treatment after diagnosis, and differences in treatment received, specifically lower likelihoods of mastectomy, radiation after surgery, and hormone therapy.

The disparity for Filipina women was largely attributable to late stage at diagnosis. Filipinas are also more likely than other Asian groups to experience obesity, which is linked to lower breast cancer survival.

The strongest predictor of breast cancer survival is stage at diagnosis, which has been linked to mammography screening. Nevada is in the lowest quartile for state mammography rates at 73 percent, compared to the U.S. average of 80 percent. Some research has shown that access to primary care is a better predictor for late stage at diagnosis than mammography rates. Nevada’s overall physician-to-population rank among U.S. states is 47th. These shortages are primarily seen in Southern Nevada, which has only 217 medical doctors (M.D.s) per 100,000 people, compared to Northwestern Nevada with of 336 M.D.s per 100,000 and the national average of 327 M.D.s per 100,000.

The Takeaway

Nevada’s goal must be to improve survival for women who do get breast cancer. Systemwide changes will be needed to see large overall gains in patient survival in Nevada, thus averting some of the 380 breast cancer deaths that occur each year among the state’s diverse women.

The new UNLV School of Medicine will be poised to play an important role in these changes. The school will welcome its first class in fall 2017. Southern Nevada has been the largest major metropolitan area in the U.S. without a public medical school. The school will bring enhanced research and clinical trial opportunities, grant funding, increases in residency and fellowship programs, and ultimately, an increase in the number and quality of physicians. Hopefully, this will serve to bridge the survival disparity between Northwestern and Southern Nevada that is also seen with other cancers.

Additionally, the UNLV School of Medicine can lead the public health community in embarking upon research-driven, culturally appropriate initiatives to improve quality across the entire continuum of breast cancer care, including expanding access to primary care, providing patient education, monitoring mammography screening by race/ethnicity, and increasing treatment according to guidelines for all patients.

About the Researchers

Dr. Paulo Pinheiro is an associate professor of epidemiology at the School of Community Health Sciences. His research focuses on cancer epidemiology, particularly the validity of epidemiological indicators for ethnic and racial minorities. Other interests include breast cancer survival disparities in Nevada, post delivery cancer in mothers, cancer in Asian subgroups, cancer follow-up methods in the U.S., childhood leukemia survival differentials, diabetes and colorectal cancer, among others. He is a state cancer registrar and works with multiple partnerships, workgroups and organizations in the fight against cancer at the local, state, national and international levels.