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Breast and Prostate Cancer, Melanoma on Rise in Area

A 25-year study shows most other types decline, but points to ethnic differences.

August 22, 2003|Thomas H. Maugh II | Times Staff Writer

The rates of most cancers are declining in Los Angeles County, but the prevalence of breast and prostate cancers and melanoma is inexplicably soaring, according to the largest cancer survey ever conducted in the region.

The prevalence rates of various cancers among ethnic groups also show "substantial and dramatic differences that offer tantalizing clues about their causes," noted physician Dennis Deapen of USC's Keck School of Medicine, coauthor of the study. For 14 different types of cancer, one ethnic group has a rate that is at least three times that of another group, he said.

Those rate differences are shrinking, however, as immigrants become acculturated, adopting eating and exercise habits more like those of native Angelenos, Deapen said.

Japanese and Filipinas, for example, show a sharp increase in breast cancer after moving to the United States, while Filipinos and Koreans suffer a significant increase in colorectal cancer.

Those are but a few of the findings of the USC cancer study. The team examined more than 700,000 cancer cases over a 25-year period to generate epidemiological data "that was not available prior to now," Deapen said.

The team included "every single cancer patient diagnosed in Los Angeles County" during a quarter century in their analysis.

The data will be especially valuable to cancer researchers because of the "incredible ethnic diversity" of the region, he added.

Overall, black men had the highest incidence of cancer at 606.9 cases per 100,000 people; Korean women had the lowest rate, 183.3 cases per 100,000.

One of the more intriguing cancers included in the study is prostate cancer, the most common cancer in men.

The rate of prostate cancer among blacks is almost 10 times as high as the rate among Koreans and at least six times as high as that among Chinese, the largest such differences observed in the study.

Little is known about the causes of prostate cancer, but researchers believe that male hormones called androgens play a role, as does genetics. Whatever the cause, the incidence of the disease has been increasing around the world since the early 1970s, said USC epidemiologist Myles M. Cockburn, coleader of the study. There was a sharp increase in prostate cancers in the late 1980s and early 1990s, attributed primarily to the introduction of the PSA test for identifying prostate tumors.

But researchers are continuing to see "really dramatic increases that are unrelated to screening," noted team member Dr. Ronald K. Ross, a urologist. "We really don't understand why," he added.

Breast cancer, the most common type among women, has remained level for most groups, but has increased rapidly among Japanese and Filipinas, who used to have low rates of the disease. Team members attributed the growth to changes in diet from the predominantly rice, fish and vegetable cuisine of their native countries to the higher-fat, lower-fiber diet that is common here. The immigrants also perform less exercise and are becoming more obese, both of which also increase breast cancer risk.

Deapen pointed out that breast cancer rates are also increasing in Japan, which is becoming culturally more like Los Angeles.

The report also noted that the incidence of melanoma, a form of skin cancer, has been growing dramatically among non-Latino whites, to the point where it has now become one of the top five cancers. Cockburn added that melanoma is readily curable when detected early.

Deapen also said that both blacks and Latinos in Los Angeles have a significant prevalence of melanoma, but that the rate is not increasing.

Among other findings of the report:

* Stomach and colorectal cancers are rapidly increasing among Koreans, Filipinos and Chinese, but declining among most other ethnic groups. Doctors suspect the increase is related to changes in diet.

* The most common cancers among Korean men are stomach and colorectal, while prostate cancer is the most common type among other ethnic groups. The difference is also believed to be related to diet.

* Lung cancer rates for most racial and ethnic groups in men are declining, although one form of the disease, adenocarcinoma, is increasing.



Cancer rates

The average annual age-adjusted incidence per 100,000 people of all cancers for combined years 1976-2000:



Latino -- 364.4

Black -- 606.9

Non-Latino white -- 517.3

Chinese -- 276.0

Japanese -- 339.3

Filipino -- 286.0

Korean -- 273.9



Latina -- 261.3

Black -- 355.4

Non-Latina white -- 409.8

Chinese -- 206.6

Japanese -- 259.7

Filipina -- 219.5

Korean -- 183.3

Source: Los Angeles Cancer Surveillance Program

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