Table 2.

Clinical Implications of Response-to-therapy Reclassification in Differentiated Thyroid Cancer Patients Treated with Total Thyroidectomy and RAI Remnant Ablation.

Category Definitions Clinical Outcomes Management Implications
Excellent Response Negative imaging
AND either
Suppressed Tg <0.2 ng/mL*
or
TSH-stimulated Tg <1 ng/mL*
1%–4% recurrence
<1% disease-specific death
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*
or
Stimulated Tg >10 ng/mL*
or
Rising Tg Ab levels
At least 30% spontaneously evolve to NED
20% achieve NED after additional therapy
20% develop structural disease
<1% disease-specific death
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 Tg antibody values should prompt additional investigations and potentially additional therapies
Structural Incomplete Response Structural or functional evidence of disease
With any Tg level
+/− Tg Ab
50%–85% continue to have persistent disease despite additional therapy
Disease-specific death rates as high as 11% with loco-regional metastases and 50% with structural distant metastases
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 Non-specific findings on imaging studies
Faint uptake in thyroid bed on RAI scanning
Non-stimulated Tg detectable, but less than 1 ng/mL
Stimulated Tg detectable, but less than 10 ng/mL
or
Tg antibodies stable or declining in the absence of structural or functional disease
15%–20% will have structural disease identified during follow-up
In the remainder, the non-specific changes are either stable, or they resolve
<1% disease-specific death
An indeterminate response should lead to continued observation with appropriate serial imaging of the non-specific lesions and serum Tg monitoring. Non-specific findings that become suspicious over time can be further evaluated with additional imaging or biopsy

Table from the ATA thyroid cancer guidelines.2 Used with permission from the American Thyroid Association.

* In the absence of Tg antibodies (Tg Ab).

NED, no evidence of disease at final follow-up.

RMMJ Rambam Maimonides Medical Journal Rambam Health Care Campus 2016 January; 7(1): e0004. ISSN: 2076-9172
Published online 2016 January 28. doi: 10.5041/RMMJ.10231.