L.A.'s ethnic diversity is credited for giving the region an edge in everything from global trade to entrepreneurial start-ups. Now, it may even be partly responsible for lower cancer rates.

Incidences of the most common forms of invasive cancer including prostate, breast, lung and colon cancer are lower in Los Angeles County than the nation as a whole, according to data compiled from 1991 to 1995 by the National Cancer Institute and USC's Cancer Surveillance Program.

Prostate cancer, for example, strikes 162.7 men per 100,000 nationwide, but only 152.3 per 100,000 in L.A. County. Among women, 110.9 per 100,000 nationally are stricken with breast cancer, compared with 99.4 per 100,000 in L.A. County.

Oncologists say environmental and lifestyle factors may play a role in the difference, but that ethnic diversity is probably responsible, too.

Los Angeles County has a large population of Asian Americans, notes Dr. Robert Nagourney, director of Rational Therapeutics, a cancer treatment facility in Long Beach. The incidence of prostate cancer among Asian Americans is half that of whites and one-third that of African-Americans, according to USC's Cancer Surveillance Program.

"In Washington D.C., where there is the highest rate of prostate cancer, you will find that they also have one of the largest populations of black men, who are the most likely to develop that type of cancer," said Nagourney, who was among those presenting studies last week at the American Society of Clinical Oncology in Los Angeles last week.

Good weather may also contribute to lower prostate cancer rates here.

"We know for prostate cancer, a sunny climate has an effect on those cancer rates because of vitamin D (from sunshine)," Nagourney said. "But there are likely some factors that are beyond environment and lifestyle that we just don't know about yet."

Smog, for example, doesn't seem tied to higher cancer rates here, said Dr. Dennis Deapen, executive director of USC's Cancer Surveillance Program.

"People think that because Los Angeles has smog, crowding or whatever, that our cancer rates are higher, but in fact they are not," said Deapen.

Deapen also said that the cancer patterns of different immigrant groups can diminish over time.

"When immigrants arrive here, they begin to assume the cancer risks of Los Angeles," Deapen said.

There also are cancer risks associated with specific areas. Nagourney noted that, until a few decades ago, workers in the Long Beach shipyards were at risk of contracting cancer from asbestos used in the shipbuilding process.

And while the Vitamin D in the sun can possibly inhibit prostate cancer, the harmful ultraviolet rays can also put people more at risk of getting melanoma, he said.

Alhough the incidences of cancer are lower here than in the nation as a whole, Los Angeles County mirrors the nation in the most common cancers. Prostate is No. 1, followed by breast, lung and colon cancer.

"We pretty much reflect the rest of the nation when it comes to cancer rates," said Dr. Wendy Cozen, an epidemiologist for the Cancer Surveillance Program for L.A. County. "The only difference is, because of the large amount of ethnic groups in L.A., we tend to find types of cancer that aren't found as often in other parts of the country."

Although neither she nor other officials had specific figures, Cozen said she suspects that Los Angeles County has higher rates for gallbladder cancer because of its large Latino population, and higher rates of AIDS-related cancers like lymphoma because of a relatively large population of AIDS sufferers.

In the state as a whole, black men are the most likely to develop and die from cancer. Latino and Asian men and women had significantly lower cancer incidence and mortality rates than their white and black counterparts, according to the "Cancer Incidence and Mortality in California by Race/Ethnicity" study compiled by the state Department of Health Services.

The study looked at cancer reporting and population estimates from 1988 to 1994.

Despite having a lower risk of developing most cancers, Asian men and women in California are two times more likely than white men and women to develop stomach cancer and five times more likely to develop liver cancer, according to the Department of Health Services.

Asian women in California have a high risk of developing invasive cervical cancer and thyroid cancer. Latino men and women also have a higher risk for stomach and liver cancer than white men and women, and Latino women have the highest rate of invasive cervical cancer overall, according to the state study.

Black men and women have twice the risk of developing stomach and liver cancer compared to white men and women, and also have twice the risk of developing multiple myeloma (bone marrow) and esophageal (throat) cancer.

Although prostate cancer (for men) and breast cancer (among women) are the most frequently diagnosed cancers, lung cancer remains the leading cause of cancer-related deaths among both men and women in California.

And of course, the primary cause of lung cancer is cigarette smoking, authorities said.

"This is not something new," Deapen said. "Clearly, cigarette smoking is the strongest known cause of a large number of cancers. When we see the smoking rates decline, 10 to 15 years later we see the cancer incidence rates decline."

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