How prevalent is thyroid cancer in the U.S.?

Though it may seem like an easy disease to track, thyroid cancer can be relatively subtle, requiring oncologists and epidemiologists to analyze reams of data in the effort to pin down its prevalence.

Several studies appearing in the past few years have attempted to quantify the rate at which thyroid cancer is diagnosed in the U.S. Most reports of this kind must address whether or not any changes to the disease's incidence are due to a wider prevalence or improved methods of detections.

Consider a paper published in the journal Cancer, which states that thyroid carcinomas are more widespread - or more broadly diagnosed - than ever before.

Written by a team of researchers from the American Cancer Society and Emory University, the report is based on several decades' worth of data collected by the National Cancer Institute (NCI).

Currently, the NCI estimates that 11 in every 100,000 Americans are diagnosed with thyroid cancer every year. This figure was once significantly lower, the new study states.

The NCI records show that between 1988 and 1998, the incidence of thyroid carcinoma diagnoses rose an average of 3.5 percent each year. Then, from 1998 to 2005, the disease's prevalence increased at an even greater rate - namely, at an average 6.7 percent annually.

What was the rate of thyroid cancer then compared to today? Researchers said that in 1988, the prevalence of the disease was 6.4 diagnoses per 100,000 women and 2.5 diagnoses per 100,000 men.

By 2005, those rates had risen to 14.9 per 100,000 women and 5.1 per 100,000 men.

The authors noted that these increases were evenly spread across tumors of all types and sizes, indicating that the true incidence of thyroid cancer may have risen (since one would not expect the largest tumors to ever have been difficult to spot).

"Reasons for this increase, including environmental, dietary and genetic causes, need to be explored. To our knowledge, there is no new evidence to suggest that the exposure of human beings to radiation, a well known environmental risk factor, has increased over time to account for the observed increase in thyroid cancer," the team added.

In a lifetime, about one in every 111 Americans will be diagnosed with thyroid cancer, the NCI states. This rate may sound relatively low, but the study's authors noted that thyroid cancer survival rates have not improved in the past two decades, indicating a need for more research into the detection of and treatments for the disease.

Certain thyroid carcinomas at least entail better prognoses than others. A study published in the journal Archives of Otolaryngology: Head and Neck Surgery found that patients with localized papillary thyroid cancer had an excellent outlook.

Those who got immediate treatment after diagnosis had a 99 percent survival rate over 20 years, while those who received delayed treatment had a 97 percent survival rate over the same period of time.