In the past I have discussed the problems with overdiagnosis and overtreatment of both mammary carcinoma in situ and prostatic adenocarcinoma. A notable third example is the overdiagnosis and overtreatment of papillary thyroid carcinoma. A recent article from JAMA Otolaryngology - Head & Neck Surgery, entitled "Current Thryoid Cancer Trends in the United States
," and published online on February 20th details this problem.
To review some findings in the article:
Since 1975, the incidence of thyroid cancer has nearly tripled, from 4.9 to 14.3 per 100,000 individuals Virtually the entire increase is attributable to papillary thyroid cancer diagnoses. The absolute increase in thyroid cancer in women was almost 4 times greater than that of men. In spite of this dramatic increase, the mortality rate from thyroid cancer has remained stable between 1975 and 2009 (approximately 0.5 deaths per 100,000).
The authors conclude that there is an ongoing epidemic of thyroid cancer in the United States. The epidemiology of the increased incidence, however, suggests that it is not an epidemic of disease but rather an epidemic of diagnosis. The problem is particularly acute for women, who have lower autopsy prevalence of thyroid cancer than men but higher cancer detection rates by a 3:1 ratio.
That there is an epidemic of overdiagnosis and not of disease is based on the facts that: The increasingly detected cancers are highly unlikely to cause symptoms or death. Despite a more than 2-fold increase in the rate of thyroid cancer detection, thyroid cancer mortality had remained stable. Virtually all of the increase was confined to a type with the least aggressive histologic characteristics, namely papillary thyroid cancer. Finally, the bulk of the increase (87%) was explained by tumors 2 cm or smaller.
It is not surprising that women have bourne the brunt of this phenomenon. Benign thyroid disease is more common in women, leading to fine needle aspirations, and surgical resections that uncover occult and largely harmless lesions. Clinicians, the article suggests, are "looking too hard" for thyroid carcinomas. Because the article is a large review based on SEER data, there is no discussion regarding what culpability pathologists might bear for this "epidemic."
The article does not distinguish between conventional papillary carcinoma, a usually straightforward diagnosis, and the follicular variant, which, as any consultant reviewing such cases will attest, is often anything but straightforward. Indeed, the latter diagnosis is associated with considerable interobserver variability and given the overall excellent prognosis, refining diagnostic criteria would require a huge database with tens of thousands of years of patient follow up.
As mentioned above, a related issue that is discussed is the diagnosis of unequivocal but very small papillary carcinomas; lesions for which the term "microcarcinoma" has been used (and I also follow this practice). The authors raise the issue of whether such lesions should carry a designation other than "carcinoma," with all its associated connotations and emotional baggage. At the very least, clinicians should share with patients the extremely indolent behavior of small papillary carcinomas, and suggest the possibility of watchful waiting as appropriate therapy. After all, this is a tumor for which we have "magic bullet" therapy if needed. The current statistic of 85% total thyroidectomy following a diagnosis of papillary carcinoma (of any type or size) is far too high.