Estimating Risk of Recurrence in Differentiated Thyroid Cancer After Total Thyroidectomy and Radioactive Iodine Remnant Ablation: Using Response to Therapy Variables to Modify the Initial Risk Estimates Predicted by the New American Thyroid Association Staging System

Abstract

Background: A risk-adapted approach to management of thyroid cancer requires risk estimates that change over time based on response to therapy and the course of the disease. The objective of this study was to validate the American Thyroid Association (ATA) risk of recurrence staging system and determine if an assessment of response to therapy during the first 2 years of follow-up can modify these initial risk estimates. Methods: This retrospective review identified 588 adult follicular cell-derived thyroid cancer patients followed for a median of 7 years (range 1-15 years) after total thyroidectomy and radioactive iodine remnant ablation. Patients were stratified according to ATA risk categories (low, intermediate, or high) as part of initial staging. Clinical data obtained during the first 2 years of follow-up (suppressed thyroglobulin [Tg], stimulated Tg, and imaging studies) were used to re-stage each patient based on response to initial therapy (excellent, acceptable, or incomplete). Clinical outcomes predicted by initial ATA risk categories were compared with revised risk estimates obtained after response to therapy variables were used to modify the initial ATA risk estimates. Results: Persistent structural disease or recurrence was identified in 3% of the low-risk, 21% of the intermediaterisk, and 68% of the high-risk patients ( p < 0.001). Re-stratification during the first 2 years of follow-up reduced the likelihood of finding persistent structural disease or recurrence to 2% in low-risk, 2% in intermediate-risk, and 14% in high-risk patients, demonstrating an excellent response to therapy (stimulated Tg < 1 ng/mL without structural evidence of disease). Conversely, an incomplete response to initial therapy (suppressed Tg > 1 ng/mL, stimulated Tg > 10 ng/mL, rising Tg values, or structural disease identification within the first 2 years of follow-up) increased the likelihood of persistent structural disease or recurrence to 13% in low-risk, 41% in intermediate-risk, and 79% in high-risk patients. Conclusions: Our data confirm that the newly proposed ATA recurrence staging system effectively predicts the risk of recurrence and persistent disease. Further, these initial ATA risk estimates can be significantly refined based on the assessment of response to initial therapy, thereby providing a dynamic risk assessment that can be used to more effectively tailor ongoing follow-up recommendations.

Undetectable pre-ablation thyroglobulin levels in patients with differentiated thyroid cancer: it is not always what it seems

“…Although undetectable pre-ablation Tg levels usually indicate complete previous surgery, our data reinforce earlier observations that, in a low percentage of patients, this situation may be related to non-detectable Tg or to the presence of TgAb (12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)31). We believe that, when concurrent chronic thyroiditis is found by the pathologist, or when initial TNM stages are diswith DTC, compared with the 10% generally seen in the general population (20).…”

“…On the other hand, undetectable Tg levels at the time of ablation may reflect variable situations, according to different publications (12,16,30,31). Almost 30% of the reported patients in these series have an undetectable Tg levels after surgery.…”

Dynamic prediction of the risk of recurrence in patients over 60 years of age with differentiated thyroid carcinoma

“…According to the literature, the significance of the re-stratification seems to be more relevant in the ATA intermediate risk category, where an excellent response to the initial treatment reduces the risk of recurrence from 18% to 2% (12). In our study, it was precisely in the ATA intermediate risk category where the re-stratification showed its real prognostic value.…”

“…As to patients with ATA (American Thyroid Association) intermediate risk, it is much more difficult to establish which will be their progression. However, if diagnostic elements are available in the first 2 years after the thyroidectomy in order to reclassify the risk according to the response to the initial treatment, this problem tends to be solved (12). This seems to happen because many intermediate risk patients, after being re-stratified, change their status to either low or high risk which is, in general, consistent with their final progress.…”

2016 Russian clinical practice guidelines for differentiated thyroid cancer diagnosis and treatment

“…Динамическая стратификация риска по-зволяет разделить пациентов на следующие четыре основные группы по результатам проведенного лечения [1, 2, 68, [134][135][136][137].…”