LITTLE FALLS, N.J., July 13 — The increasing incidence of thyroid cancer in the U.S. is more than the result of better screening, researchers said.

• Explain that incidence rates of thyroid cancer increased among tumors of all sizes — not just the smallest ones, which would be expected if the increase was attributable to increased screening alone.
• Note that the researchers call for the investigation of other potential explanations, including diet, environmental influences, and molecular pathways.

Incidence rates rose for tumors of all sizes — not just the smallest ones, as it would if more cases were simply being caught by increased screening, Amy Y. Chen, MD, MPH, and colleagues reported online in Cancer.

“Our finding that even the largest tumors and tumors with distant spread of disease had an increasing incidence suggests that other reasons for this increase, including environmental, dietary, and genetic causes, need to be explored,” the researchers said.

Previous studies have found an increasing incidence of thyroid cancer, and some researchers have pointed to increased detection through more widespread and aggressive use of ultrasound and image-guided biopsy.

But increasing incidence rates can also reflect a true increase in the number of cancers, the researchers said.

So, to determine potential causes of the increase, researchers looked at data on 30,766 thyroid cancer patients from the Surveillance, Epidemiology, and End Results (SEER) study. All were diagnosed between 1988 and 2005.

Mortality rates were unchanged over that period, despite higher rates of diagnosis, the researchers said.

Among women, incidence of thyroid cancer increased from 6.4 per 100,000 to 14.9 per 100,000, while incidence among men increased from 2.5 per 100,000 to 5.1 per 100,000.

Although the highest rate of increase was for tumors under 1 cm (P<0.001), there were significant increases in all tumor sizes, particularly those greater than 4 cm, they noted.

The researchers reported no conflicts of interest.

Primary source: Cancer

Source reference:
Chen AY, et al “Increasing incidence of differentiated thyroid cancer in the United States, 1988-2005″ Cancer 2009; DOI: 10.1002/cncr.24416.

Several statistical and biological issues need to be addressed in order to improve biomarker identification for early detection of cancer, according to a commentary published online July 2 in the Journal of the National Cancer Institute.

The biomarker pipeline to develop and evaluate cancer screening tests includes the identification of promising biomarkers to detect cancers early and the initial and definitive evaluation of biomarkers for cancer screening.

In the commentary, Stuart G. Baker, ScD, of the National Cancer Institute in Bethesda, Md., discusses the various ways to improve this pipeline, including the need for more frequent specimen collection to help identify promising biomarkers and the use of the paired availability design, in which data are collected on the number of interval cases associated with screening in time periods before and after the introduction of the new biomarker test.

“…[S]ome important design and analysis considerations related to this biomarker pipeline have been underappreciated, insufficiently disseminated, or not previously discussed,” the author writes. “By taking these considerations into account, researchers can improve this biomarker pipeline.”

Source:
Steve Graff

Journal of the National Cancer Institute