The Steady Rise in Thyroid Cancer
Researchers still baffled by tripling of cases over 30 years
"The question has been answered," Frank said. "It is not just a matter of better detection. But it is unclear why there is an increase in true incidence."
For the most common type of thyroid cancer, the prognosis is generally excellent, he noted. "Younger patients do the best, but older patients still generally do well," Frank added. "But older patients -- generally those over age 50 -- with more advanced disease, with metastatic or large tumors, do not always do so well in terms of disease recurrence and ultimate survival, although they can still do quite well and survive."
For the study, Goldenberg's team compared the clinical and pathologic characteristics of 31 patients whose thyroid cancer was discovered when they had diagnostic imaging for reasons other than thyroid cancer with 207 patients who had scans specifically to diagnose thyroid cancer.
Men accounted for more than half of those whose cancer was discovered incidentally (54.8 percent) but only 13.5 percent of those screened specifically for thyroid cancer, the researchers found.
Average age at diagnosis was about 42 for those scanned for thyroid cancer and 56 for those diagnosed incidentally. The cancers found in an unrelated scan were more advanced, but no difference between the groups was noted in tumor size, amount of cancer inside the thyroid, or cancer that had spread to the lymph nodes or other organs.
But if better detection isn't behind the uptick in cases, what is?
Goldenberg has looked at exposure to radiation and radon as possible contributors.
"We recently published our work looking into the Three Mile Island vicinity as an etiological [causative] factor -- no association found," Goldenberg said. The Three Mile Island accident was a partial meltdown of a nuclear reactor in central Pennsylvania in 1979. "We recently completed a study looking at radon as a causative factor -- no association found," he said.
The researchers said they need to study whether other lifestyle and environmental factors are contributing to the increase in thyroid cancer.