br Analysis br Unadjusted counts of papillary
Unadjusted counts of papillary thyroid cases and age-adjusted incidence rates per 100,000 with 95% confidence intervals were calculated using SEER*Stat 8.3.4).38 The incidence rates were standardized to the US 2000 population. In addition, we also computed proportions of various surgery types among the total number of papillary cases. We examined the trends in incidence rates and in the proportion of the PTCs by tumor size and tumor stage. Annual percentage changes (APCs) were used to quantify the trends in incidence rates. We used the Kendall’s tau correlation tests for trend analysis in Stata 14.2 (StataCorp, College Station, TX). Tau, a rank-based procedure, measures the monotonic relationship between incidence rates and year. Using the case-wise listing for the first matched cases, we used the data to report the odds ratio of having total thyroidectomy or thyroid lobectomy in bivariate and multivariable logistic regression analysis.
Table III exhibits results from bivariate and multivariable ana-lyses of total thyroidectomy versus thyroid lobectomy. Bivariate analysis demonstrated that men were more likely to undergo total thyroidectomy than women (odds ratio OR : 1.09 [95% confidence interval CI : 1.02e1.17], P ¼ .014). Similarly, we found that compared with age group 40 to 59 years, patients under 40 years of
Sample characteristics, age-adjusted incidence rates, and adjusted odds ratio (AOR) of papillary thyroid cancer (SEER 9 Registries, 2000e2014)
Characteristics Count Rates (95% CI) APC AOR (95% CI) P value
Thyroid cancer size (cm)
APC, annual percentage change; REF, reference.
* P value < .001 based on the significance testing for annual percent change (APC) for age-adjusted incidence of papillary thyroid cancer during the study GelRed (2000e2014).
Fig 1. Incidence and proportion of total thyroidectomy versus thyroid lobectomy for papillary thyroid cancer. Each solid line represents the proportion of total thyroidectomy versus thyroid lobectomy during the study period. Each dotted line represents the change in incidence of total thyroidectomy versus thyroid lobectomy during the study period. Vertical dotted lines represent the dates of the ATA guideline changes.
age in the bivariate analysis were more likely to undergo total thyroidectomy for any size cancer, whereas patients older than 59 years of age were more likely to receive thyroid lobectomy. This relationship remains the same for older age groups in the
multivariable model. We observed no racial differences in surgical approach. Cases from the non-Appalachian region were less likely to receive total thyroidectomy (OR: 0.54 [95% CI: 0.43e0.68], P <
Fig 2. Incidence and proportion of total thyroidectomy versus thyroid lobectomy for papillary thyroid cancer by size (< 1 cm, 1e2 cm, 2e4 cm, and > 4 cm). Each solid line represents the proportion of total thyroidectomy versus thyroid lobectomy during the study period. Each dotted line represents the change in incidence of total thyroidectomy versus thyroid lobectomy during the study period. Vertical dotted lines represent the dates of the ATA guideline changes.
Annual percent change in proportion of surgeries among all papillary thyroid cancer cases by tumor size from 2000 to 2014
In the multivariable analysis, after adjusting for the effect of age, sex, race, and Appalachian region, we found that compared with large (4þ cm) tumors, smaller (e4 cm) tumors were more likely to undergo total thyroidectomy (P < .001). Compared with localized stage, regional and distal stages of papillary cancer were signifi-cantly more likely to have total thyroidectomy than thyroid lo-bectomy (P < .001).
These findings confirm that throughout the past 15 years in the United States, the incidence of PTC has increased
substantially.1,3 Because patient mortality has remained stable, there is concern that this rise may be attributed to over-diagnosis because of increased medical screening, and subse-
quent care may carry the risks of overtreatment of pseudodisease.39,40 Both in 2006 and 2009, the ATA guidelines
on the treatment of PTC shifted recommendations in the treatment of low-risk, small (1e1.5 cm) thyroid cancers to consider thyroid lobectomy and isthmusectomy as definitive surgical treatment. This shift was further endorsed for tumors up to 4 cm by the American Association of Clinical Endocri-nologists in 2015.36 During our study period, the proportion of total thyroidectomy among all papillary cases increased to 85.7%, and the proportion of thyroid lobectomy dropped to 11.4%. Because the study period encompasses two iterations of changes in the guidelines published by the ATA along with the development of molecular markers supporting less aggressive surgical treatment, we believe the lack of change in surgical management overall reflects delayed adoption and uptake of less-invasive approaches to low-risk disease.