Since the 1970s, physicians have used age of diagnosis to determine the severity of thyroid cancers. Papillary thyroid cancers -- those including affected lymph nodes -- diagnosed before age 45 are designated as stage I, following the American Joint Committee on Cancer and the International Union Against Cancer TNM Classification of Malignant Tumors staging system.
The same papillary thyroid cancer with lymph node involvement presenting after age 45 years is considered stage III.
With 34,000 new cases of papillary thyroid cancer diagnosed annually, researchers from Thomas Jefferson University Hospital set out to determine the scientific validity of diagnosis at 45 years of age and older as such a powerful negative prognosticator.
"While this staging system was once accurate and effective, we are seeing that patients age 45 to 64 have similar outcomes to those under age 45 years," said Jeffrey L. Miller, MD, the co-director of the Thyroid Center at Thomas Jefferson University Hospital and lead researcher on the study.
A review of the literature determined that this age marker was first set forth in a study in 1979, followed by a paper in 1993 reviewing 1,779 patients treated for papillary thyroid cancer from 1940 to 1989 to determine the variables most prognostic of mortality. When looking at age, the mortality curve seemed most pronounced in patients older than age 60. A 2005 study showed significant declines in mortality in patients older than age 45, though no statistics for other age ranges were given.
The Jefferson team subsequently analyzed thyroid cancers diagnosed between 2001 and 2007 in the Surveillance, Epidemiology and End Result (SEER) database and reviewed five-year survival rates. Of the 45,390 cases reviewed, the most significant drop in survival rate was seen in those age 65 to 74 years, though prognosis was still good at 92%. An even more marked survival difference was noted in those diagnosed with thyroid cancer at age 75 and older at 82%.
"With time, we have developed new therapies and surgical techniques, leading to better survival rates," Dr. Miller concluded. "This leads many patients to have a more favorable prognosis, avoid potentially unnecessary therapies and allay patients' fears about their longevity up to age 64. We feel that age 45 is no longer an appropriate age designation to influence papillary thyroid cancer prognosis."
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