Cancer clusters controversies confusing communities

August 3, 2009

While there is no evidence to suggest that cancer clusters are becoming more common in Australia, concerns about them need to be taken seriously, according to one of Australia’s foremost authorities on the subject.

Associate Professor Tim Driscoll, an epidemiologist and a specialist in occupational medicine from the University of Sydney, is one of Australia’s leading investigators into cancer clusters, a term used to describe a higher than expected rate of cancer or cases of cancer in a particular group.

Cancer clusters will be put under the microscope at a free public talk by Assoc Prof Driscoll in Perth on August 3 as part of the annual Cancer Council Update series.

Assoc Prof Driscoll who conducted an investigation at the National Gallery of Australia from 2006 to 2008, said none of the cancer cluster investigations in Australia in the last 10 years have identified any cancer cause in the workplace or community for the cancer cases that occurred.

However cancer clusters are exceptionally difficult to investigate because in some areas you do expect higher rates of cancer due to random and lifestyle factors,” said Assoc Prof Driscoll.

“Often investigators don’t get the definitive answer that people would like.”

Investigations into cancer clusters focus on the exposures and the type and rate of cancers that have occurred.  They also look at when the cancers occurred in relation to possible cancer causes at the suspect site.

“Nearly always when people have concerns about a cancer cluster in a particular area, investigators cannot identify any source of an exposure that could explain the high rate of cancer,” said Assoc Prof Driscoll.

He said if investigators find a high rate of cancer but no exposure then it’s almost certain that the high rate has occurred by chance, but even then it may be tricky to decide what to do.  This was the situation in Australia’s most high profile cancer cluster case at the ABC in Brisbane. 

“Cancer is a common disease that occurs randomly, so you can expect just through chance some areas can have high rates of cancer and some can have low.”

However Assoc Prof Driscoll said concerns about cancer clusters shouldn’t be dismissed.                                         
“It’s important that investigations don’t just look at the scientific evidence, but also consider social factors including why people are concerned,” he said. 

“It’s very important that concerns about cancer clusters are not ignored, because if you don’t look, you leave a group of people who are very worried.”

At the very least, he said, investigations into cancer clusters will give people confidence that there are no problem exposures now, or if problems are identified, then they can be fixed.

More generally, Assoc Prof Driscoll said people should remember that the best thing they can do to avoid cancer is to focus on the known risk factors, such as ensuring they exercise, have a healthy diet, reduce their exposure to the sun and don’t smoke.

For further information on cancer clusters or the Cancer Council Update series call the Cancer Council Helpine 13 11 20.