Too much fuss over thyroid

VITAL SIGNS

To the shock of many cancer experts, the most common cancer now in South Korea is thyroid cancer, whose incidence has increased fifteenfold in the past two decades.

Similar upward trends for thyroid cancer are found in the United States and Europe, although not to the same degree.

Cancer experts agree that the reason for the situation in South Korea and elsewhere is not a real increase in the disease.

Instead, it is down to screening, which is finding tiny and harmless tumours that are better left undisturbed, but that are being treated aggressively.

South Koreans embraced screening about 15 years ago when the government started a national programme for a variety of cancers - breast, cervix, colon, stomach and liver.

In the United States and Europe, where there are no formal, widespread screening programmes for thyroid cancer, scans for other conditions like ultrasound exams of the carotid artery in the neck or CT scans of the chest are finding tiny thyroid tumours.

Although more and more small thyroid cancers are being found, the death rate has
remained rock steady, and low. If early detection were saving lives, death rates should have come down.

That pattern tells researchers that many of the cancers they were finding and treating were not dangerous.

It is a phenomenon that researchers call overdiagnosis, finding cancers that did not need to be found because they grow very slowly or not at all. Left alone, they would probably never cause problems.

Overdiagnosis is difficult to combat. Pathologists cannot tell which small tumors are dangerous, and most people hear the word “cancer” and do not want to take a chance.
But cancer experts said the situation in South Korea should be a message to the rest of the world about the serious consequences that large-scale screening of healthy people can have.