Cancer in context: 37 years of painstakingly collected data

Prostate and lung cancer have been the No. 1 and 2 cancers among men. Stomach cancer, the third leading cause of cancer deaths worldwide, has been on a steady decline among Koreans and Japanese. Black men had the highest overall rates of cancer. Thyroid cancer—which is relatively treatable—has been on the rise, and women are about three times more likely to contract it than men.

These are a few of the notable nuggets in the most recent "Cancer in Los Angeles County: Trends by Race/Ethnicity 1976-2012," a book released on Aug. 15. The report card includes every cancer diagnosis in the region over the past 37 years—more than 1.3 million. With easy-to-read charts, the book divides L.A.'s population into 11 ethnic and racial groups to highlight the fact that cancer risk is a result of genetics, environment and behavior.

"Not only are we are telling people what has happened to others in the past, but we are also helping them understand their own future cancer risk," said Dennis Deapen, the report's senior author and a professor of preventive medicine at the Keck School of Medicine of USC. "The majority of cancer in Los Angeles is preventable: You can reduce the risk yourself. Let this be a reminder to get appropriate checkups to help identify any cancer early."

The Los Angeles Cancer Surveillance Program (CSP), a state-mandated database managed by Keck Medicine of USC and the USC Norris Comprehensive Cancer Center, provides scientists everywhere with essential statistics on cancer. About two publications each day cite this large and diverse databank as a resource, said Deapen, who directs the program.

USC's report card provides evidence of how environmental and lifestyle choices can alter one's cancer risk. For instance, Asian women living in Los Angeles experience higher and continuously rising breast cancer risk compared to their counterparts living in Asia. That's because breast cancer is more prevalent in developed countries with westernized lifestyles, said Lihua Liu, lead author and an assistant professor of preventive medicine at Keck Medicine of USC.

"The message for immigrant populations is very clear," Liu said. "When they come to this country, their lifestyle changes affect their cancer risk."

Liu noted that while immigrants' risk generally increases for cancers that are common in this country, their risk for others common in their home countries—like stomach and liver cancer—decreases.

"The general explanation is the exposures to risk factors associated with specific infections and lifestyle choices change once immigrants leave their home country," Liu said. "For example, prevalence of H. pylori and HBV infections is much lower in the U.S. than in Asian countries. Both are major risk factors for stomach and liver cancers, respectively."

The scientific jury is still out when it comes to the impact of specific lifestyle factors, including dietary patterns, but Liu said the changing cancer risks among different immigrant populations can provide valuable information for better understanding and better control of cancer.

Why Los Angeles' cancer data is significant

Los Angeles is the most populous county in America. It houses about 9 percent of the country's Latinos and Asian-Americans—two of the fastest-growing demographics in the nation.

Annually, some 41,000 new cancer diagnoses are added to the CSP database, which can provide an overview of cancer incidence patterns in different population groups and generate rosters of patients so that scientists know who to invite to participate in cancer research. The current report card is the third L.A. County cancer report card since 2003.

"Although we still don't know the whole picture of causes for every cancer, as scientists, our goal is to reveal the existing but often hidden cancer risk patterns," Liu said. "The next question is what's the difference between a low-risk group versus a high-risk group. If we know that, we may be able to help."

The main message is that many cancers are preventable and, if caught early, are curable, Deapen said. In general, cancers of the prostate, cervix, esophagus and lung are on the decline.

"We are greatly encouraged to see the steady decline in the rate of deaths due to cancer, which was not true in the first 20 years of the CSP," Deapen said. "It is great to see so many people understand that they can take action when it comes to cancer risk."

A sampling of L.A. County cancer trends in context of the past 37 years

• Black men had the highest overall rates of cancer and, on average, were twice as likely to be diagnosed with cancer when compared to most Asian subgroups. Blacks have the highest risk of developing cancer of the prostate, pancreas, kidney, multiple myeloma, esophagus and larynx.
• In general, prostate and lung cancer were the No. 1 and 2 cancers among men. For Vietnamese men, however, lung cancer was the top cancer. Interestingly, lung cancer is declining at a faster pace than colorectal cancer, which means colorectal cancer eventually could become the most common cancer among Vietnamese men.
• In general, breast cancer followed by colorectal cancer are the two most common cancers among women. In recent years, breast cancer has been declining or plateauing, except among Korean women, who are experiencing an increase.
• Most of the top five cancers in Latino, black and white men are declining or have remained unchanged. Melanoma is the exception; it continues to increase, especially among whites.
• Kidney and renal pelvis cancers have increased among blacks, Hispanics and whites over the past 40 years. Increasing adult obesity rates in L.A. County may be the reason for this hike; however, the observed increase also could be attributed to improved diagnosis rather than a true increase in cancer risk.
• In the past decade, thyroid cancer—which is relatively treatable—has been on the rise. Women are about three times more likely to get it than men. The climb is steepest among Filipinos and whites.
• Stomach cancer, the third leading cause of cancer deaths worldwide, has been on a steady decline among Koreans and Japanese, who are most at-risk for stomach tumors.