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Why is thyroid cancer increasing? – QIMR researchers investigate


QIMR scientists have received funding to investigate a large increase in cases of thyroid cancer in Australia in the past 25 years.

Lead investigator, Dr Susan Jordan, said the incidence of thyroid cancer had increased by 350% between 1982 and 2008.

Dr Jordan’s team has just secured National Health and Medical Research Council (NHMRC) funding to investigate what might be causing the increase.

The Australian Institute of Health and Welfare (AIHW) says 1 in 138 people will be diagnosed with thyroid cancer by the time they are 75. About 460 Queenslanders are diagnosed each year.

Dr Jordan said there were several theories as to why the cancer is on the increase.

“The causes of thyroid cancer are largely unknown. The suggestion is that there may be environmental factors driving that increase,” Dr Jordan said.

“The best known cause of thyroid cancer is early exposure to high doses of radiation, for example in children who need radiation treatment for cancer. But radiation treatment for childhood cancer can’t really explain the rise in thyroid cancer, so other causes need to be considered.

“There is some concern that increasing use of diagnostic radiation, particularly CT scans, is problematic, although there’s no strong evidence at this point.”

The other possible cause for the increase in thyroid cancer diagnosis is that slow-growing thyroid cancers are being diagnosed more often.

“There are particular types of thyroid cancer that are slow growing. They might sit in your thyroid and not become apparent at any point in your lifetime. In the past, cancers like that wouldn’t have been picked up, whereas they are nowadays, because people are simply having more tests for other, unrelated conditions,” Dr Jordan said.

“The problem is that, once detected, we have no way of telling if a tumour is aggressive. It needs to be treated, usually by surgically removing the thyroid, then giving the patient radioactive iodine therapy.”

Dr Jordan’s team will investigate risk factors for thyroid cancer as well as the ways in which people come to be diagnosed with the disease. She believes that determining whether or not a particular gene mutation (BRAF) is present in the cancer will help to unravel the causes.

“If we can separate the different types of thyroid cancer and their causes, we’ll have a clearer picture of what’s happening,” Dr Jordan said.

The QIMR team have received funding from the NHMRC to recruit 1,000 newly-diagnosed thyroid cancer patients to a four-year study.

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