Acknowledging gray areas: 2015 vs. 2009 American Thyroid Association differentiated thyroid cancer guidelines on ablating putatively low-intermediate-risk patients.

PURPOSE: Typically formulated by investigators from "world centres of excellence," differentiated thyroid carcinoma (DTC) management guidelines may have more limited applicability in settings of less expert care and fewer resources. Arguably the world's leading DTC guidelines are those of the American Thyroid Association, revised in 2009 ("ATA 2009") and 2015 ("ATA 2015"). To further explore the issue of "real-world applicability" of DTC guidelines, we retrospectively compared indications for ablation using ATA 2015 versus ATA 2009 in a two-centre cohort of ablated T1-2, M0 DTC patients (N = 336). Based on TNM status and histology, these patients were low-intermediate risk, but many ultimately had other characteristics suggesting elevated or uncertain risk. METHODS: Working by consensus, two experienced nuclear medicine physicians considered patient and treatment characteristics to classify each case as having "no indication," a "possible indication," or a "clear indication" for ablation according to ATA 2009 or ATA 2015. The physicians also identified reasons for classification changes between ATA 2015 versus ATA 2009. Classification was unblinded, but the physicians had cared for only 138/336 patients, and the charts encompassed September 2010-October 2013, several years before the classification was performed. RESULTS: One hundred of 336 patients (29.8 %) changed classification regarding indication for ablation using ATA 2015 versus ATA 2009. Most reclassified patients (70/100) moved from "no indication" or "clear indication" to "possible indication." Reflecting this phenomenon, "possible indication" became the largest category according to the ATA 2015 classification (141/336, 42.0 %, versus 96/336, 28.6 %, according to ATA 2009). Many reclassifications were attributable to multiple clinicopathological characteristics, most commonly, stimulated thyroglobulin or anti-thyroglobulin antibody levels, multifocality, bilateral involvement, or capsular/nodal invasion. CONCLUSIONS: Regarding indications for ablation, ATA 2015 appears to better "acknowledge grey areas," i.e., patients with ambiguous or unavailable data requiring individualised, nuanced decision-making, than does ATA 2009.

Difficulties in deciding whether to ablate patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma: do guidelines mainly apply in the centres that produce them? Results of a retrospective, two-centre quality assurance study.

PURPOSE: We determined the reasons for radioiodine thyroid remnant ablation, and the procedure's necessity based on postsurgical remnant size, in patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma (DTC). We identified key clinicopathological, treatment and remnant characteristics, and factors associated with remnant size in 336 patients with pT1/2, M0 DTC ablated during the period September 2010 to October 2013 at one Cypriot or one Greek referral centre. METHODS: Clinicopathological/treatment characteristics were compiled from charts. Experienced nuclear medicine physicians rated the numbers/intensities of uptake foci in the thyroid bed on postablation planar scintigrams using scales of 0-4 points and 0-3 points, respectively. The product of these scores was taken as the "remnant score" that ranged from 0 (no remnant) to 12 (multiple remnants, intense uptake). RESULTS: DTC was predominantly papillary. The median [25th-75th percentile] longest primary tumour diameter was 1.0 cm [0.7-1.5 cm]. Despite favourable histotypes and primary tumour classifications, patients often had preablation characteristics suggesting elevated or uncertain risk: 31.0% of patients (104 of 336) had primary tumour multifocality, 22.0% (74) had confirmed cervical lymph node metastases, 37.2% (125) had unknown nodal status, and 38.1% (128) had antithyroglobulin antibody seropositivity. The median [25th-75th percentile] remnant score was 4 [2-6]; 39.9% of patients (134 of 336) had scores ≥6. For the entire cohort, T or N stages (r ≤ 0.174, P ≤ 0.05) correlated positively with the remnant score in a univariate Spearman analysis. The numbers of patients referred by the surgeon, cervical lymph nodes excised and metastatic nodes excised correlated negatively (r ≤ 0.243, P ≤ 0.038) with the remnant score, and the first two factors independently predicted the remnant score (P ≤ 0.037) in a multivariate analysis. CONCLUSION: Patients with putatively "low-intermediate-risk" DTC frequently had disease characteristics denoting high or uncertain risk, suggesting that "selective" radioiodine ablation in such patients may seldom be applicable outside international centres of excellence. Proxies for surgeon experience and surgical completeness correlated with remnant number/uptake intensity and may aid ablation-related decision-making.