Rising incidence of thyroid cancer cannot be explained by improvements in screening and detection

August 7, 2009 at 11:59 am | Posted in News | Leave a comment
Follicular adenoma of the thyroid. Image: Wikimedia Commons

Follicular adenoma of the thyroid. Image: Wikimedia Commons

Anyone who enjoyed August’s feature on rising cancer incidence might find the following two studies interesting.

Both conclude that rising rates of thyroid cancer cannot be put down to improved screening – leaving the question, what is responsible for the rise in incidence?

Increasing incidence of differentiated thyroid cancer in the United States, 1988-2005

Chen AY, Jemal A, Ward EM. Health Services Research, American Cancer Society/Emory University, Atlanta, Georgia.

BACKGROUND:: Studies have reported an increasing incidence of thyroid cancer since 1980. One possible explanation for this trend is increased detection through more widespread and aggressive use of ultrasound and image-guided biopsy. Increases resulting from increased detection are most likely to involve small primary tumors rather than larger tumors, which often present as palpable thyroid masses. The objective of the current study was to investigate the trends in increasing incidence of differentiated (papillary and follicular) thyroid cancer by size, age, race, and sex.

METHODS:: Cases of differentiated thyroid cancer (1988-2005) were analyzed using the National Cancer Institute’s Surveillance Epidemiology and End Results (SEER) dataset. Trends in incidence rates of papillary and follicular cancer, race, age, sex, primary tumor size (<1.0 cm, 1.0-2.9 cm, 3.0-3.9 cm, and >4 cm), and SEER stage (localized, regional, distant) were analyzed using joinpoint regression and reported as the annual percentage change (APC).

RESULTS:: Incidence rates increased for all sizes of tumors. Among men and women of all ages, the highest rate of increase was for primary tumors <1.0 cm among men (1997-2005: APC, 9.9) and women (1988-2005: APC, 8.6). Trends were similar between whites and blacks. Significant increases also were observed for tumors >/=4 cm among men (1988-2005: APC, 3.7) and women (1988-2005: APC, 5.70) and for distant SEER stage disease among men (APC, 3.7) and women (APC, 2.3).

CONCLUSIONS:: The incidence rates of differentiated thyroid cancers of all sizes increased between 1988 and 2005 in both men and women. The increased incidence across all tumor sizes suggested that increased diagnostic scrutiny is not the sole explanation. Other explanations, including environmental influences and molecular pathways, should be investigated.

Cancer 2009. (c) 2009 American Cancer Society.

Rising thyroid cancer incidence in the United States by demographic and tumor characteristics, 1980-2005

Enewold L, Zhu K, Ron E, Marrogi AJ, Stojadinovic A, Peoples GE, Devesa SS. United States Military Cancer Institute, Department of Pathology and Area Laboratory Service, Walter Reed Army Medical Center, Washington, DC 20306-6000, USA. Lindsey.Enewold@us.army.mil

Thyroid cancer incidence has been rising in the United States, and this trend has often been attributed to heightened medical surveillance and the use of improved diagnostics.

Thyroid cancer incidence varies by sex and race/ethnicity, and these factors also influence access to and utilization of healthcare.

We therefore examined thyroid cancer incidence rates by demographic and tumor characteristics based on 48,403 thyroid cancer patients diagnosed during 1980-2005 from the Surveillance, Epidemiology and End Results program of the National Cancer Institute.

The rates varied by histologic type, sex, and race/ethnicity. Papillary carcinoma was the only histologic type for which incidence rates increased consistently among all racial/ethnic groups. Subsequent analyses focused on the 39,706 papillary thyroid cancers diagnosed during this period.

Papillary carcinoma rates increased most rapidly among females. Between 1992-1995 and 2003-2005, they increased nearly 100% among White non-Hispanics and Black females but only 20% to 50% among White Hispanics, Asian/Pacific Islanders, and Black males.

The increases were most rapid for localized stage and small tumors; however, rates also increased for large tumors and tumors of regional and distant stage.

Since 1992-1995, half the overall increase in papillary carcinoma rates was due to increasing rates of very small (<or=1.0 cm) cancers, 30% to cancers 1.1 to 2 cm, and 20% to cancers>2 cm.

Among White females, the rate of increase for cancers>5 cm almost equaled that for the smallest cancers. Medical surveillance and more sensitive diagnostic procedures cannot completely explain the observed increases in papillary thyroid cancer rates.

Thus, other possible explanations should be explored.

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