Thyroid Cancer - Critical Threat?

February 03, 2015| By Ross Campbell | Critical Illness | English

Being told of the first sign of a cancer with deadly potential, but which early treatment may cure, is a medical reassurance anyone would be relieved to receive. The benefit of detection is less clear when the detected “cancer” is most likely harmless and will pose no health threat. This may trigger only anxiety and perhaps lead to unnecessary treatment.

Strong arguments support cancer screening in a clinical setting, but for insurers offering Critical Illness (CI) policies it could mean they receive claims for tiny tumours that are anything but serious. Affordable access to sensitive imaging technology has the potential to drive a massive rise in the numbers of insignificant cancers being detected.

Proof of the potential for screening to distort the CI landscape is to be found further afield. Thyroid cancer, for example, has been uncommon in the past but global incidence rates have been increasing dramatically. The nation with the highest levels of papillary thyroid cancer is South Korea.

South Korea embarked on a national screening programme in 1999 focused on finding and then treating cancer of the breast, cervix, liver and colon. The chance to extend peace of mind by adding a thyroid scan, at small personal cost, has proved irresistible to many. Unfortunately, this has exposed (in huge numbers) an underlying reservoir of tiny thyroid cancers long known to exist in the general population from the evidence of autopsy studies.

The explosion of thyroid cancer in South Korea is not the result of sinister medical mutation or exposure to environmental hazards. What has been experienced is an “epidemic of diagnosis” of a non-life threatening condition. At least this is the conclusion of a scientist behind a recent study published in the New England Journal of Medicine1.

One of the co-authors, Professor H. Gilbert Welch, then wrote an opinion column in the New York Times, calling for greater attention to be paid to monitoring “more important risks to health”. To underline the point that increased screening has not saved more lives, he stated that the mortality from thyroid cancer in South Korea has not increased during 20 years.

That this epidemic of diagnosis has not been followed by a steep rise in related mortality is simply explained. The majority of tumours detected this way are “microcarcinomas” – below one centimeter in size – and therefore unlikely to develop or to threaten life. Cancer claims are payable under CI policy conditions regardless of any such threat.

It is of relevance to CI definitions that there is no stage 0, pre-invasive stage or carcinoma-in-situ in the accepted staging systems of thyroid cancer. This means that tissue is either described as “benign” or “malignant” with no pre-malignant category in the histological classification. This has clear implications for CI claims.

Despite increasing incidence of thyroid cancer, the very low mortality rate makes it unlikely that national screening programmes would be introduced to detect it. However, radiological imaging with CT or MRI scanning has increased significantly in recent years. If this reveals a thyroid lesion as an incidental finding, it is hard to avoid further investigation, including a biopsy, even when any subsequent health benefit is low.

Screening makes perfect sense for people whose family history suggests they are at high risk of cancer. Early detection of sinister malignancy undoubtedly saves lives. Yet the incidental detection of indolent tumours of insignificant size may actually do more harm than good. In South Korea it has led to an increase in surgical removal of the thyroid, triggering life-long treatment to replace the vital hormones this gland provides.

The disparity between rising incidence and flat mortality rates supports the conclusion the thyroid cancer is over-diagnosed. It is about time that our CI definitions recognized the advances in medical screening and adopted exclusions to maintain the relevance and affordability of the product going forward.

This article was originally published in Cover magazine.

1. Hyeong Sik An, Hyun Jung Kim and H. Gilbert Welch “Korea’s thyroid cancer 'epidemic' – screening and overdiagnosis” N ENGL J MED 2014, 371:1765-1767.


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