. 2016 Jan 1;26(1):1–133. doi: 10.1089/thy.2015.0020

Table 13.

Clinical Implications of Response to Therapy Reclassification in Patients with Differentiated Thyroid Cancer Treated with Total Thyroidectomy and Radioiodine Remnant Ablation

Category	Definitions^a	Clinical outcomes	Management implications
Excellent response	Negative imaging *and either* Suppressed Tg <0.2 ng/mL^b or TSH-stimulated Tg <1 ng/mL^b	1%–4% recurrence^c<1% disease specific death^c	An excellent response to therapy should lead to an early decrease in the intensity and frequency of follow up and the degree of TSH suppression
Biochemical incomplete response	Negative imaging *and* Suppressed Tg ≥1 ng/mL^b or Stimulated Tg ≥10 ng/mL^bor Rising anti-Tg antibody levels	At least 30% spontaneously evolve to NED^d 20% achieve NED after additional therapy^a 20% develop structural disease^a <1% disease specific death^a	If associated with stable or declining serum Tg values, a biochemical incomplete response should lead to continued observation with ongoing TSH suppression in most patients. Rising Tg or anti-Tg antibody values should prompt additional investigations and potentially additional therapies.
Structural incomplete response	Structural or functional evidence of disease With any Tg level With or without anti-Tg antibodies	50%–85% continue to have persistent disease despite additional therapy^e Disease specific death rates as high as 11% with loco-regional metastases and 50% with structural distant metastases^a	A structural incomplete response may lead to additional treatments or ongoing observation depending on multiple clinico-pathologic factors including the size, location, rate of growth, RAI avidity, ¹⁸FDG avidity, and specific pathology of the structural lesions.
Indeterminate response	Nonspecific findings on imaging studies Faint uptake in thyroid bed on RAI scanning Nonstimulated Tg detectable, but <1 ng/mL Stimulated Tg detectable, but <10 ng/mL or Anti-Tg antibodies stable or declining in the absence of structural or functional disease	15%–20% will have structural disease identified during follow-up^a In the remainder, the nonspecific changes are either stable, or resolve^a <1% disease specific death^a	An indeterminate response should lead to continued observation with appropriate serial imaging of the nonspecific lesions and serum Tg monitoring. Nonspecific findings that become suspicious over time can be further evaluated with additional imaging or biopsy.

NED denotes a patient as having no evidence of disease at final follow-up.

^{^a}

References (538,539).

^{^b}

In the absence of anti-Tg antibodies.

^{^c}

References (538,539,542,586–593,595–601,1078).

^{^d}

References (598,599,617–621).

^{^e}

References (328,607,626,627,898).