Study draws bead on prostate ills

By LOUISE THOMAS

New Zealand has the sixth-highest rate of prostate cancer in the world.

It is the most common cancer among men and there are 500 deaths a year here as a result of the disease.

With the ageing population, it has been estimated that deaths could increase to more than 1100 a year over the next 20 years.

However, research in the United States may help stem the tide of prostate cancer deaths with advances in a standard diagnostic tool, the prostate specific antigen (PSA) test.

Researchers have found a marked difference in the levels of the antigen between black American men and those of European descent. Black American men have been found to have a higher normal level of it in their blood.

Work is now starting here to establish normal PSA levels for Pakeha, Maori and Pacific Islanders.

PSA level has long been used as the standard test by general practitioners when a man suspects he is having trouble with his prostate. If a blood test shows high antigen levels, it could be an early warning sign of prostate cancer and he can be referred for further diagnosis.

In response to the American findings, a collaborative team from Otago University's Wellington School of Medicine including public health, surgery and pathology will be conducting a two-year community study to examine PSA levels.

This should be useful knowledge for the use of PSA in initial diagnosis, because the normal reference range could differ between ethnic groups.

"We want to see if there is a difference between the three groups in their normal levels of PSA," says project coordinator Marion Gray. "If there are not, the diagnostics we've been using to date are fine, but no studies of this type have been done in New Zealand."

The study will also attempt to raise awareness of the disease, particularly in the Pacific Island and Maori populations.

The reasons for New Zealand's prevalence of prostate cancer are largely unknown but are probably linked to diet and family history.

"Japanese men, for example, have the lowest rate of prostate disease in the world," says Ms Gray. "But when Japanese men move to the States that sub-group shows a marked increase in the cancer."

However, exactly which factors are involved is unknown. Some research has shown that high fat intake is a factor, but then other studies will come along to counter this.

"It is believed that a family predisposition, combined with diet, are contributors with most hormone-based cancers, such as breast and prostate," says Ms Gray.

The study aims to examine 1950 blood samples, taken from 650 men between the age of 40 and 70 years from Maori, Pakeha and Pacific Island groups.

The samples will be taken from the Wellington area, where a series of hui and meetings have already been held to explain the study.

Participants will be asked to submit to a simple blood test and answer questions about symptoms, diet, occupation and family history of prostate problems. Men who test positive to the PSA blood screening or have symptoms will be asked to visit their family doctor for further diagnosis and, if necessary, treatment.

Ms Gray says the initial consultation with the family doctor will be funded by the study.

"We have based ourselves in the community and are working in partnership with various community groups to ensure that the study gets done and that the community benefits from it.

"Some of the Maori health providers have offered us use of their clinics so we can do the testing in the community. Hopefully this way we'll get a good response rate, people will be more comfortable going to a place they are familiar with and to take part in a study they have heard about through their own community."

Ms Gray says they are particularly concerned about the rate of prostate cancer among Pacific Island men.