Cancer Counts

Disparities in cancer rates among racial and ethnic groups in Los Angeles County point out declining and increasing cancers and subgroups at high risk

Melanoma has increased so rapidly in Los Angeles County in the past two decades that it is now one of the area’s top five most common cancers, according to statistics from the Los Angeles Cancer Surveillance Program based at the USC/Norris Comprehensive Cancer Center.

That is just one glimpse into surprising findings from the report “Cancer in Los Angeles County: Trends by Race/Ethnicity,” an examination of 25 years of local cancer data. Produced by the Los Angeles Cancer Surveillance Program, or CSP, which collects and analyzes information on all new cancers diagnosed in the county, the report points out how different cancers have affected various ethnic groups over time.

The report is the first widespread study to examine cancer incidence rates in specific ethnic communities, such as the Japanese and the Koreans. It probes the nature of cancer in changing populations through a lens that only a place such as Los Angeles—the most populous and ethnically diverse county in the nation—can provide. And it is the longest and largest study of its kind in Los Angeles, comprising more than 700,000 cancer cases.

By gender, the report shows that black men and non-Latino white women are hardest hit, proportionately, by cancer. But cancer rates vary significantly by gender and ethnicity: For 14 different kinds of cancer, one ethnic or racial group had at least three times greater incidence of that cancer than another ethnic or racial group.

“Observing these changing rates of cancer incidence helps us generate new hypotheses about the causes of cancer, and to identify population subgroups at high risk of developing various cancers,” says Dennis Deapen, Dr.P.H., professor of clinical preventive medicine at the Keck School of Medicine of USC and CSP director.

A sampling of the trends includes the following:

• Breast cancer, the most common cancer among women, increased rapidly among Japanese and Filipinas (who used to have low rates of the disease), while it remained level for other groups. Researchers believe this increase might be due to increasing Western acculturation and a movement away from a potentially protective

diet and lifestyle.

• Stomach cancer rates declined among non-Latino whites, blacks, Latinos and Japanese, but increased among Filipinos, Koreans and Chinese. This might be due to differing immigration patterns, since stomach cancer rates are higher in the Philippines, Korea and China than in Los Angeles.

• Prostate cancer was the most common male cancer, except among Korean men. Prostate cancer rates generally peaked and plateaued after the prostate-specific antigen, or PSA, test was introduced. The rates among black men in Los Angeles, however, appear to be continuing to increase.

• Melanoma rates continue to increase for reasons that remain unclear. Although melanoma is usually rare in non-white populations, there is a significant prevalence of the disease in Latinos and blacks in Los Angeles.

• Filipinas were the only group to have increasing rates of thyroid cancer.

• Testicular cancer increased rapidly among non-Latino whites and Latinos but remained rare among other racial and ethnic groups.

• Colorectal cancer rates, traditionally lower among Filipinos and Koreans, are increasing among these groups, as well as among Japanese. Rates for blacks, Latinos and non-Latino whites are declining.

Because Los Angeles is a microcosm of the nation’s shifting demographics and represents a wide spectrum of cultures, the report may provide clues for a better understanding of cancer nationwide. It will also help identify aspects of lifestyle that raise or lower the risk of certain cancers—factors that could have great impact on public health.