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