Lead researcher Dr Diana Sarfati describes the results as “very interesting” as they run counter to overseas studies in this area.
The New Zealand results show that Maori men have much higher rates of testicular cancer than non-Maori, and that men from lower-socioeconomic groups also have higher rates.
“This is opposite to the rest of the developed world where wealthy white men tend to have the highest rates of this cancer,” says Dr Sarfati. “However in New Zealand, Maori men have 50% more testicular cancer than European New Zealanders, while Asian and Pacific men have 50% less than Europeans.
“Whilst we should not expect rates by ethnicity in New Zealand to mirror image those of different ethnic groups in other countries, the fact that Māori rates are higher than European New Zealanders is curious in light of international data,” says Sarfati.
Dr Sarfati says the study did not look at the reasons behind these differences. Testicular cancer rates are increasing in all developed countries and it remains unclear why this is so, and why some groups have higher rates than others. There has been speculation that these trends relate to hormonal exposures in prenatal or early life, but so far the aetiology of testicular cancer is largely unknown.
The New Zealand study is based on all 2000 cases of testicular cancer taken from the Cancer Registry among men aged 15-44 years since 1981, and linked to census data. It is part of a larger study headed by Professor Tony Blakely, investigating ethnic and socioeconomic trends in cancer incidence in New Zealand, CancerTrends.
Testicular cancer is mainly a disease of young men, but has an excellent survival rate because it responds well to surgery and chemotherapy.
“Nevertheless for young men and teenagers in particular this is a particularly traumatic disease, which takes quite a toll on their confidence and needs to be carefully managed,” says Dr Sarfati.
The study did not find that there were obvious and large changes in differences in testicular cancer between ethnic and socioeconomic groups from 1981 to 2004. If trends truly vary by ethnic and socioeconomic group, it may only become apparent with longer time series. But Sarfati says the overall New Zealand rates are similar to many other developed countries overseas.
“We need to carry out further investigation into why New Zealand is so different from the rest of the developed world in terms of patterns of testicular cancer following these intriguing results,” she says.
This study has been funded by the Health Research Council and published in the International Journal of Cancer.
For further information please contact
Dr Diana Sarfati
Department of Public Health
University of Otago, Wellington
Tel 64 4 918 6042