Some patients with low-risk thyroid cancer are undergoing unnecessary treatment, experts have warned.
A dramatic rise in the number of thyroid cancer cases at a time when death rates remain stable is “most likely an effect of over-diagnosis”, they said.
The number of people diagnosed with thyroid cancer in England has doubled since the early 1990s, according to data from the National Cancer Intelligence Network (NCIN).
Between 1990 and 1994, around 900 people were diagnosed with thyroid cancer every year in England. But figures from 2006 to 2010 showed a jump to 1,950 cases a year.
Most of this increase is in a particular type of thyroid cancer called papillary cancer.
The rise has been linked to increased diagnosis of the disease due to techniques such as ultrasound and fine needle biopsies that can pick up much smaller cancers.
But experts writing in the British Medical Journal (BMJ) said picking up these papillary cancers “usually triggers intensive treatment”, even though they are unlikely to lead to an early death.
“This is exposing patients to treatments inconsistent with their prognosis,” said the team from the Mayo Clinic in Minnesota, US.
“Both the overdiagnosis and over-treatment of this form of cancer need to be fully recognised.”
Dr Claire Knight, health information manager at Cancer Research UK, said: “Like the US, England has seen a dramatic rise in the number of thyroid cancer cases diagnosed over previous decades.
“Much of this increase has been among papillary thyroid cancers, a type which has a very good prognosis.
“It’s not clear whether this increase is due to more people actually developing the disease, and if so why, or if it’s down to better imaging and diagnostics picking up cancers which may never have gone on to cause a person harm - this is called overdiagnosis.
“It’s important that researchers and doctors are aware that overdiagnosis of thyroid cancer is a real concern and that patients, particularly those with papillary thyroid cancer, are able to discuss treatment options with their doctor.
“More research will help us understand the biology of thyroid cancer, which cancers need treating, and which are so slow-growing that they will not cause a person any harm.”
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