State Cancer Rate Varies Widely by Region, Study Finds : Health: Most types occur less frequently in L.A. and Orange counties than in other areas surveyed. Experts say environmental factors may not explain the differences.

A new study of cancer rates in California shows sharp differences from region to region, but experts caution against concluding that exposure to pollution or other environmental factors can explain the variations.

Preliminary results of the state Department of Health Services cancer survey released Monday show that the overall incidence of cancer in the state is lower than that in the nation as a whole.

And most types of cancer occur at a lower rate in Los Angeles and Orange counties than in the other regions of the state included in the survey--Sacramento, the San Francisco Bay Area and the Central Valley.

But William Wright, chief of research for the state tumor registry, which produced the findings, said regional differences in the 1987 data may be explained by known cancer risk factors, including smoking habits and ethnic and racial background.

“Some of these differences are known to be due to the differences in population,” Wright said.

For example, the lung cancer rate for men in Orange County is the lowest of the five regions--with 62 cases per 100,000 population in 1987. That is 27% lower than in the Central Valley and Sacramento, which had 85 cases per 100,000.

But Wright said 80% or more of lung cancers are thought to be smoking-related. And one explanation of the high lung cancer rate in Sacramento may be that large numbers of former military personnel have moved into the area for their retirement, he said, “bringing their cancer risks with them.”

Retired military personnel are more likely to be smokers, in part, Wright said, because of the practice of tobacco companies making free cigarettes available to troops during wartime.

The Department of Health Services is now planning a telephone survey of smoking habits, comparing Sacramento County with another area in the state to determine if differences in smoking rates can explain the differences in cancer. “An earlier study on smoking prevalence has convinced us that we will find those differences,” Wright said.

The Los Angeles area also has one of the lowest rates of breast cancer in the state, 93 cases per 100,000 for the study year compared with 113 cases in the San Francisco Bay Area, according to the state survey.

But Los Angeles County has large Latino and Asian populations--two groups known to have a lower risk of breast cancer than other racial and ethnic groups, Wright said. Differences in lifestyle--diet and number of children, for example--may explain the differences.

Wright said state health officials are still awaiting U.S. Census results on the racial and ethnic mix in each of the five regions to see if they can explain the latest findings.

Overall, Los Angeles County has the lowest cancer rate in the state--311 cases per 100,000 population in 1987, followed by Orange County with 315 per 100,000. The San Francisco Bay Area had the highest overall rate--373 per 100,000, which is well above the average of 333 for the five regions.

The overall cancer rate for the nation as a whole in 1987 was 377 cases--higher than any of the five regions included in the California survey.

The figures have been corrected to take into account differences in the age of the population in each area of the state, since the risk of cancer increases with age.

The statewide tumor registry was established in 1985 in an effort to get detailed information on cancer cases throughout the state. The 1987 survey was limited to five regions, but 1988 results, which cover the entire state, are scheduled for release later this month.