br cancers PTCs e Although multiple factors
cancers (PTCs).3e5 Although multiple factors may be contributing to a true rise in the incidence of thyroid cancer, such as exposure to flame-retardant chemicals and am increased use of diagnostic radiography, the majority of this Actinomycin D increase has been attributed to incidentally found thyroid cancers.1,6 This explanation is further supported by a multitude of pathologic studies demonstrating incidentally found thyroid cancers on autopsy.7e10 Moreover,
multiple studies have shown that this change in incidence has not been associated with a change in mortality.1,5,11 This finding gains more significance when placed in the context of the significant
financial and psychologic burden attributed to thyroid cancer treatment.12e17
Before the early 2000s, the standard surgical treatment of thy-roid cancer, regardless of size, was a total thyroidectomy. This approach was supported by a large retrospective study using the National Cancer Data Base of more than 50,000 patients, presenting a lower recurrence rate and increased survival in patients who underwent total thyroidectomy compared with thyroid lobec-tomy.18 However, further studies failed to replicate these findings.19e26 Additional arguments for a more aggressive surgical approach include the ability to subsequently treat with radioactive iodine and detect recurrence using thyroglobulin, both of which require total thyroidectomy to be utilized. However, the use of radioactive iodine has not been substantiated in small, nonag-gressive PTCs.27e30 Along with the considerable data showing equivalency in outcomes with less aggressive surgery, there have also been several studies showing significant quality of life effects associated with the treatment of thyroid cancer, primarily thy-
roidectomy and radioiodine ablation, suggesting a true detrimental effect of overtreating these less aggressive thyroid cancers.15,16,31e33
As a result of the growing body of literature suggesting over-diagnosis and overtreatment of nonaggressive PTCs, a substantial shift in the recommendations for the surgical treatment have occurred during the past 12 years. In 2006, the American Thyroid Association (ATA) guidelines shifted to recommending thyroid lo-bectomy for low-risk PTCs smaller than 1 cm.34 In 2009, the ATA guidelines further expanded the recommendation for thyroid lo-bectomy to cancers smaller than or equal to 1.5 cm.35 More recent guidelines from other organizations have recommended thyroid lobectomy as safe for the treatment of PTCs up to 4 cm in size.36 To evaluate the effects of changing guidelines, we describe the recent practice patterns in the United States in total thyroidectomy and thyroid lobectomy for PTC based on size.
Materials and Methods
Data on thyroid cancer incidence, histology, size distribution, and surgical treatment were obtained from the Surveillance, Epidemiology, and End Results (SEER)*Stat database.37 This pro-gram is maintained by the National Cancer Institute, which began collecting data in 1973. Of the 18 SEER registries, 9 registries (Atlanta Metropolitan, Connecticut, Detroit Metropolitan, Hawaii, Iowa, New Mexico, San Francisco-Oakland, Seattle-Puget Sound, and Utah) were chosen to represent roughly 10% of the US popu-lation and provide long-term incidence data since 1973.
Tumor definitions, characteristics, extent of surgery
Histologically confirmed thyroid cancer cases from 2000 to 2014 were included. Thyroid cancer cases, as defined by the International Classification of Diseases for Oncology, 3rd ed and WHO 2008 site recode C739, were identified. Of those thyroid cases, we restricted our sample to include only papillary thyroid cases (Histologic Type ICD-O-3: 8050, 8052, 8130, 8260, 8340-8344, 8450-8452) that were histologically confirmed and not reported from death certificate or autopsy only. All cases labelled “in situ,” benign, were excluded from the analysis. Only the first matching record for each person was selected for each case. Based on the histologic criteria, we excluded 11.8% (n ¼ 5,950) of the thyroid cases that were not PTCs.
For all included cases, the overall incidence of thyroid cancer was evaluated. In addition, we analyzed cases by tumor size grouped into < 1 cm, 1e2 cm, 2e4 cm, and 4 cm þ. We also grouped the PTC by SEER Historic Stage A into localized, regional, and distant, which is derived from Collaborative Stage (CS) for 2004 þ and Extent of Disease (EOD) 1973 to 2003. Surgery was grouped
into two categories: total thyroidectomy and thyroid lobectomy. Total thyroidectomy included those coded as subtotal thyroidec-tomy, near total thyroidectomy, or total thyroidectomy or thyroid-ectomy, not otherwise specified. Thyroid lobectomy included those coded as thyroid lobectomy or isthmusectomy. Additional data collected included sex, race or ethnicity, age at diagnosis, and residence in the Appalachian region.