Led by researchers at the University of Pittsburgh School of Medicine, an international panel of pathologists and clinicians has reclassified a type of thyroid cancer to reflect that it is noninvasive and has a low risk of recurrence. The name change, described today in JAMA Oncology, is expected to reduce the psychological and medical consequences of a cancer diagnosis, potentially affecting thousands of people worldwide.
The incidence of thyroid cancer has been rising partly due to early detection of tumors that are indolent or non-progressing, despite the presence of certain cellular abnormalities that are traditionally considered cancerous, explained senior investigator Yuri Nikiforov, M.D., Ph.D., professor of pathology and director of Pitt's Division of Molecular and Genomic Pathology.
"This phenomenon is known as overdiagnosis," Dr. Nikiforov said. "To my knowledge, this is the first time in the modern era a type of cancer is being reclassified as a non-cancer. I hope that it will set an example for other expert groups to address nomenclature of various cancer types that have indolent behavior to prevent inappropriate and costly treatment."
In particular, a tumor type known as encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) has increased in incidence by an estimated two- to three-fold over the past 20 to 30 years and makes up 10 to 20 percent of all thyroid cancers diagnosed in Europe and North America, the panel noted. Although studies have shown EFVPTC is not dangerous, it is typically treated as aggressively as other types of thyroid cancer. At the recommendation of the National Cancer Institute, the panel sought to revise the terminology and to see if the word "cancer" could be dropped from its name.
Two dozen experienced pathologists from seven countries and four continents independently reviewed 268 tumor samples diagnosed as EFVPTC from 13 institutions. The experts established diagnostic criteria, including cellular features, tumor invasion and other factors. In a group of more than 100 noninvasive EFVPTCs, there were no recurrences or other manifestations of the disease at a median follow-up of 13 years, the panel found.
These experts decided to rename EFVPTC as "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" or NIFTP. The new name cites key features to guide pathologists in diagnosis, but omits the word "cancer," indicating that it need not be treated with radioiodine or other aggressive approaches.
"We determined that if NIFTP is carefully diagnosed, the tumor's recurrence rate is extremely low, likely less than 1 percent within the first 15 years," Dr. Nikiforov said. "The cost of treating thyroid cancer in 2013 was estimated to exceed $1.6 billion in the U.S. Not only does the reclassification eliminate the psychological impact of the diagnosis of 'cancer,' it reduces the likelihood of complications of total thyroid removal, and the overall cost of health care."
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