Growing incidence of thyroid carcinoma in recent years: Factors underlying overdiagnosis

Abstract

There is an increasing incidence of well-differentiated thyroid cancer worldwide. Much of the increase is secondary to increased detection of small, low-risk tumors, with questionable clinical significance. This review addresses the factors that contribute to the increasing incidence and considers environmental, and patient-based and clinician-led influences. Articles addressing the causes of the increased incidence were critically reviewed. A complex interplay of environmental, medical, and social pressures has resulted in increased awareness of the thyroid disease risk, increased screening of thyroid cancers, and increased diagnosis of thyroid cancers. Although there is evidence to suggest that the true disease incidence may be changing slightly, most of the increase is related to factors that promote early diagnosis of low-risk lesions, which is resulting in a significant phenomenon of overdiagnosis. An improved understanding of these pressures at a global level will enable healthcare policymakers to react appropriately to this challenge in the future.

Thyroid cancer in adolescents and young adults

“…The dramatic increase in TC incidence has not concurred with a change in the TC mortality rate, with the annual TC death rate in 15–49 year‐olds in the US remaining steady between 0.1 and 0.2 per 100,000 for each year during 1990–2015 (Figure , lower panel). The reason for this disassociation could be that an increase in the death rate has yet, after a quarter century, to become apparent.…”

“…Most AYAs with TC are still treated according to approaches used in adult patients rather than per guidelines of the American Thyroid Association (ATA) . As reviewed here, the diagnosis of TC from a biopsy must be evaluated assiduously relative to its potential to be truly malignant, a problem that has been occurring worldwide …”

“…5 As reviewed here, the diagnosis of TC from a biopsy must be evaluated assiduously relative to its potential to be truly malignant, a problem that has been occurring worldwide. [6][7][8][9] Abbreviations: ATA, American Thyroid Association; AYA, adolescent and young adult; CT, computed tomography; CTN, calcitonin; DTC, differentiated TC; FMTC, multigenerational familial medullary thyroid cancer; FNAB, fine-needle aspiration biopsy; FTC, follicular thyroid cancer; HD, Hodgkin lymphoma; MEN, multiple endocrine neoplasia; MTC, medullary thyroid cancer; PTC, papillary thyroid cancer; RAI, radioiodine; RET, rearranged during transfection; TC, thyroid cancer; TKI, tyrosine kinase inhibitors; TSH, thyroid stimulating hormone; US, ultrasound; VEGFR, vascular endothelial growth factor receptor F I G U R E 1 Annual thyroid cancer incidence in AYAs 15-39 years of age, 1992-2014 (upper panel), and mortality rate in year-olds, 1992-2015 (upper panel), U.S. SEER13. The incidence regressions are exponential and the mortality regression is linear.…”

“…There were too few deaths in females and males for mortality rate assessment. *Additional 10 years beyond the standard AYA interval of 15-39 years to include older AYAs dying of thyroid cancer (source: US NCI SEER program 13 ) The dramatic increase in TC incidence has not concurred with a change in the TC mortality rate, [6][7][8][9] with the annual TC death rate in year-olds in the US remaining steady between 0.1 and 0.2 per 100,000 for each year during 1990-2015 ( Figure 1, lower panel). The reason for this disassociation could be that an increase in the death rate has yet, after a quarter century, to become apparent.…”

Refining definitions within low‐risk differentiated thyroid cancers

“…They are often found incidentally, are thought to be present in a significant number of asymptomatic patients and represent minimal if any risk to survival and a very low risk of recurrence. 9 Excision with thyroid lobectomy is often sufficient treatment for such cases and efforts are being made to identify those patients who may even benefit from avoiding surgery altogether. [10][11][12] The remaining patients lie in a low-risk group.…”