Thyroid radiation doses are much too high

["Fred Dawson" <fd003f0606@blueyonder.co.uk>]

New Scientist reports 6 March that Thyroid radiation doses are much too high







Millions of people with thyroid disease are being given excessive doses of

radiation that could increase their risk of contracting cancer. That's the

conclusion of the Swedish Radiation Protection Authority (SSI), which says

many hospitals around the world are ignoring international recommendations

to minimize patients' exposure to radiation.



Up to 5 per cent of women and a much smaller proportion of men contract

Graves disease, an immune system defect causing the thyroid gland to produce

too much hormone. For 50 years the disease has been treated by destroying

all or part of the gland with radioactive iodine-131.







But Helene Jonsson, an SSI inspector, says doctors fail to optimise the

radiation dose for individuals, as they do with X-rays and CT scans. "With

iodine therapy, they don't care," she told New Scientist. "It is a concern."







Patients are commonly given a fixed amount of iodine-131, often 370

megabecquerels, without taking into account the size of the thyroid gland,

the amount of iodine it takes up and the amount it loses, Jonsson says. All

of these can vary widely, and Jonsson is particularly worried about young

people being treated in this way because their chances of developing cancer

as a result in later life are higher. She says some children in the US have

been given large fixed doses of Iodine-131,  which she describes as

"horrible".







To test how much difference it makes to calculate the dose individually,

Jonsson analysed 187 cases of Graves disease at Maimo University Hospital

between 1984 and 1988 in which doses of Iodine-131 were individually

optimised. She worked out that if the patients had instead been exposed to a

fixed 370 megabecquerels they would have received an average of two-and-a-

half times as much radiation as they needed (Radiation Protection Dosimetry,

vol 108, p 107).







That, Jonsson argues, would breach the recommendation by the International

Commission on "Iodine-131 is highly toxic to young children, increasing the

risk of thyroid cancer even at low doses" Radiological Protection to keep

radiation exposure "as low as reasonably achievable". For countries in the

European Union, it would also be a breach of a 1997 directive protecting

people against the dangers of medical radiation.







Keith Baverstock, an expert on radiation and health at the University of

Kuopio in Finland, agrees there is cause for concern. "Iodine-131 is highly

toxic to young children, increasing the risk of thyroid cancer even at low

doses," he says.







Dan Ash, president of the Royal College of Radiologists in the UK, agrees it

is important to keep radiation doses as low as possible. "It is likely that

some patients will get more than they need," he says." But that is better

than failing to treat the disease, especially when there is no proof that

the treatment causes long-term damage to health” Rob Edwards







Fred Dawson

New Malden

Surrey. KT3 5BP

England



020 8287 2176





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