Natural Course of the American Thyroid Association Response to Therapy Statuses (Dynamic Risk Stratification) in Differentiated Thyroid Cancer

Prognostic role and characteristics of the indeterminate response in differentiated thyroid cancer: a systematic review

PURPOSE

The management of differentiated thyroid cancer (DTC) is actually based on a dynamic risk stratification based on classes of response to the therapy. Indeterminate response (IR) includes a heterogeneous group of patients with different characteristics, particularly different Tg and AbTg levels and/or imaging findings. The aim of systematic review (SR) is to evaluate the prognosis, diagnostic findings and other characteristics of patients in the IR class.

METHODS

A wide literature search in the Scopus, PubMed/MEDLINE and Web of Science databases was performed to find published articles on patients with DTC and IR after treatment. The quality assessment of studies was carried out using QUADAS-2 evaluation.

RESULTS

Eight articles were included in the systematic review. Six studies evaluated the prognosis and the prognostic factor in patients with IR, one study evaluated the role of 2-[18F]FDG PET-CT in the management of patients with IR and biochemical incomplete response and one study the risk factors for IR.

CONCLUSION

Patients with DTC and IR to therapy have a probability of disease relapse < 15%. Tg value could be a predictor of disease progression. The role of 2-[18F]FDG PET-CT needs to be further investigated.

Is Stimulated Thyroglobulin Before Radioiodine Therapy a Useful Tool in Predicting Response to Initial Therapy in Patients with Differentiated Thyroid Carcinoma?

Thyroglobulin (Tg) is an important tool to evaluate the persistence and recurrence risk in differentiated thyroid cancer (DTC). We aimed to evaluate the correlation between pre-radioiodine therapy stimulated Tg (pre-RAI Tg) levels and the first response to treatment evaluation, and to establish a cut-off pre-RAI Tg threshold for predicting an initial excellent response. Retrospective cohort study of DTC patients who underwent total thyroidectomy and radioiodine therapy. Response to therapy was evaluated 6 to 24 months after initial therapy, and patients were classified as: excellent response (ER); indeterminate response (IndR) and incomplete response (IncR). Total patients: 166 among which 85.5% female with mean age of 47.6 ± 13 years. The ER had a significantly lower pre-RAI Tg in comparison to IndR (p<0.001) and IncR (p<0.001), and pre-RAI Tg were different between the IndR and IncR (p=0.02). A cut-off pre-RAI Tg value at 7.55ng/ml was obtained by receiver operating characteristics curve for differentiating ER from IndR and IncR. The area under curve was 0.832 (95% CI 0.76-0.91). In multivariate analysis, ATA low-risk (RR 1.61, 95% CI 1.06-2.43, p=0.025) and Tg below 7.55ng/ml (RR 2.17, 95% CI 1.52-3.10, p<0.001) were associated with ER. After a median of 7.4-year follow-up, 124 (74.7%) patients were allocated into ER, 22 (13.2%) into IndR, and 20 (12%) into IncR. In conclusion, pre-RAI Tg predicts first evaluation of treatment response. Pre-RAI Tg cut-off was a key predictor of initial excellent response to therapy and may be an important tool in the follow-up of DTC patients.

Basal or stimulated thyroglobulin in evaluating response to treatment in papillary thyroid carcinoma? A retrospective cohort study

OBJECTIVE

It is not clear whether response to initial treatment in papillary thyroid carcinoma (PTC) patients is best evaluated by measuring thyroglobulin (Tg) in the presence of levothyroxine (BTg) or when stimulated by elevated TSH (STg). The aim of this study was to evaluate whether response to therapy 1 year after initial treatment changes with the use of STg in relation to BTg in PTC patients treated with total thyroidectomy (TT) and radioiodine (131I), and, if observed, to assess which response is better associated with clinical course.

SUBJECTS AND METHODS

This is a retrospective study of 148 PTC patients submitted to TT and 131I. We analyzed the response to therapy (excellent, biochemical incomplete, or indeterminate) at 1 year after initial treatment, using BTg or STg, and compared which method was better associated with "excellent response at final evaluation."

RESULTS

Twenty-eight patients (20.4%) presented change in response to therapy, with 17 of these (60.7%) presenting a worse response. Response using STg was 1.6 times better associated with proposed outcome [odds ratio (OR) = 4.61; confidence interval 95% (IC95%): 2.13-9.98] than with BTg (OR = 2.84; IC95%: 1.33-6.06).

CONCLUSION

Response to therapy at 1 year using STg was altered in approximately 20% of cases and therefore proved to be a better predictor of excellent response in the last evaluation.

Impact of the number of intermediate risk factors on outcome of papillary thyroid cancer

PURPOSE

The 2015 American Thyroid Association risk stratification system (2015-RSS) is used to assess the tumor recurrence rate and guide the initial treatment. At the current moment, patients with one or multiple intermediate risk factors (IRF) have the same treatment. This study was conducted to evaluate the impact of the number of IRF characteristics on tumor persistence or recurrence rates.

METHODS

Patients with intermediate risk papillary thyroid cancer (PTC) were selected and analyzed, furthermore, they were divided into two subgroups, one with 1-2 IRF and another with ≥3 IRF. Those data were analyzed in relation to response to therapy at the end of the first year and in last appointment, time to reach non evidence of disease (NED) state and time in NED state.

RESULTS

A total of 257 patients were evaluated. Extrathyroidal invasion, vascular invasion, the total number of IRF and the subgroup of ≥3 IRF were associated with non-excellent response in last consultation; IRF lymph node metastasis was associated with non-excellent response in the first year and in last appointment and prolonged time in NED state; vascular invasion was associated with a shorter time in NED state; total number of IRF and aggressive histology were related to delay in the achievement of NED state.

CONCLUSIONS

Higher number of IRF was a predictive factor of non-excellent response in the last visit and was associated with longer time to reach the NED state. Those data suggest a benefit from closer follow-up and more intensive treatment in these patients.

Comparison of Prognostic Value Between Stimulated and Nonstimulated Thyroglobulins in Differentiated Thyroid Cancer: A Retrospective Study

Purpose

The growing incidence of differentiated thyroid cancer (DTC) demands dependable prognostic factors to guide follow-up and treatment plans. This study investigated the prognostic value of response to therapy (RTT) assessment using TSH stimulated-thyroglobulin (sti-Tg) and nonstimulated-thyroglobulin (nonsti-Tg) and evaluates whether RTT using nonsti-Tg (nonstiRTT) can replace RTT using sti-Tg (stiRTT) in clinical practice to improve patients' quality of life during assessment.

Methods

We enrolled 419 DTC patients who underwent total thyroidectomy, radioactive iodine (RAI) therapy, and Tg assessment. Patients with structural incomplete responses were excluded. Initial RTT assessments based on the 2015 American Thyroid Association guidelines (excellent response; ER, indeterminate response, biochemical incomplete response) were performed 6-24 months after RAI therapy. The second RTT assessments were performed 6-24 months after the first assessment. Statistical analysis for recurrence-free survival (RFS) was done with the log-rank test for stiRTT and nonstiRTT.

Results

Although initial stiRTT and nonstiRTT were significant predictors for RFS (p < 0.0001), stiRTT provided better RFS prediction than nonstiRTT. The RFS analysis of the second RTT assessment demonstrated statistical significance only for stiRTT (p < 0.0001). In 116 patients classified as ER on initial stiRTT, there was no RFS difference between patients classified as ER on either second stiRTT or nonstiRTT.

Conclusion

The prognostic power of stiRTT surpasses that of nonstiRTT in both the initial and second RTT assessment. Nevertheless, among patients classified as ER on initial stiRTT, a second stiRTT may not be required for those classified as ER on the second nonstiRTT.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13139-023-00811-8.

Usefulness of second 131I treatment in biochemical persistent differentiated thyroid cancer patients

Background

Second 131I treatment is commonly performed in clinical practice in patients with differentiated thyroid cancer and biochemical incomplete or indeterminate response (BiR/InR) after initial treatment.

Objective

The objective of the is study is to evaluate the clinical impact of the second 131I treatment in BiR/InR patients and analyze the predictive factors for structural incomplete response (SiR).

Patients and methods

One hundred fifty-three BiR/InR patients after initial treatment who received a second 131I treatment were included in the study. The clinical response in a short- and medium- long-term follow-up was evaluated.

Results

After the second 131I treatment (median 8 months), 11.8% patients showed excellent response (ER), 17% SiR, while BiR/InR persisted in 71.2%. Less than half (38.5%) of SiR patients had radioiodine-avid metastases. Patients who, following the second 131I treatment, experienced SiR had larger tumor size and more frequently aggressive histology and vascular invasion than those experienced BiR/InR and ER. Also, the median values of thyroglobulin on levothyroxine therapy (LT4-Tg), Tg peak after recombinant human TSH stimulation (rhTSH-Tg) and thyroglobulin antibodies (TgAb) were significantly higher in patients who developed SiR. At last evaluation (median: 9.9 years), BiR/InR persisted in 57.5%, while 26.2% and 16.3% of the patients showed ER and SiR, respectively. About half of BiR/InR patients (71/153 (46.4%)) received further treatments after the second 131I treatment.

Conclusions

Radioiodine-avid metastatic disease detected by the second 131I is an infrequent finding in patients with BiR/InR after initial treatment. However, specific pathologic and biochemical features allow to better identify those cases with higher probability of developing SiR, thus improving the clinical effectiveness of performing a second 131I treatment.

Risk Stratification of Differentiated Thyroid Cancer: A Single-Center Study in Basrah

Background Differentiated thyroid cancer is a common endocrine cancer; most of it has an indolent course and favorable outcomes, with a subset of patients having the risk of disease recurrence, which can be assessed using the fixed American Thyroid Association (ATA) risk stratification system or the dynamic response to therapy risk stratification that can be modified during patients follow-up. Aim The aim of this article is to assess the risk stratification of patients having differentiated thyroid cancer. Methods This is a retrospective cross-sectional study in which we evaluated medical records of 75 patients having differentiated thyroid cancer to assess the baseline ATA risk of recurrence and compared it to the results of dynamic risk stratification in response to therapy at 6-12 months post-surgery and at the last visit. Thyroglobulin level, anti-thyroglobulin antibody, thyroid ultrasound, and cytopathological examination were used to determine dynamic response to therapy and divided subjects into four groups: excellent response (ER), biochemical incomplete response (BIR), structural incomplete response (SIR), and indeterminate response (IR). Results At baseline, 55 patients had low risk, 14 patients had intermediate risk, and six patients had high risk. At 6-12 months post-surgery, in the low-risk group, ER, BIR, and IR responses were observed in 56.4%, 5.5%, and 38.2% of patients, respectively, and none of them exhibited SIR. In the intermediate-risk group, ER, BIR, and IR responses were observed in 57.1%, 21.4%, and 21.4% of patients, respectively, and none exhibited SIR. Among the high-risk group, two patients had ER, two patients had BIR, one patient had IR, and one patient had SIR. At the last visit, ER, BIR, and IR were observed in 65.5%, 9.1%, and 25.5% of low-risk patients, respectively, and no patient developed SIR. In the intermediate-risk group, ER, BIR, and IR were observed in 50%, 21.4%, and 28.6% of patients, respectively, and no patients developed SIR. Among the high-risk group, three patients achieved ER, one had BIR, one had IR, and one had SIR. Conclusion Most of the differentiated thyroid cancers in this study are low-risk. Dynamic risk stratification appears to be an effective tool in the follow-up of this population of patients having differentiated thyroid cancer.

Dynamic Risk Stratification Integrated with ATA Risk System for Predicting Long-Term Outcome in Papillary Thyroid Cancer

BACKGROUND

In recent years, there has been a renewed interest in thyroid cancer management paradigms that use individualized risk assessments as the basis for treatment and follow-up recommendations. In this study, we assumed that the long-term follow-up of differentiated thyroid cancer patients might be better tailored by integrating the response to initial therapy with the America Thyroid Association (ATA) risk classes.

METHODS

This retrospective study included low- and intermediate-risk papillary thyroid cancer (PTC) patients followed up for a median time of 8 years and classified according to the response to initial therapy assessed 6-12 months after initial treatment.

RESULTS

After a median follow-up of 8 years, in the initial excellent response subgroup of PTC patients (n = 522), the rate of recurrent disease was significantly higher in intermediate-risk patients than in low-risk PTC patients (6.9% versus 1.2%, p = 0.0005). Similarly, in the initial biochemical incomplete response subgroup (n = 82), the rate of excellent response was significantly higher in low-risk PTC patients (58.0%) than in intermediate-risk PTC patients (33.3%) (p = 0.007). Finally, in the initial structural incomplete response subgroup (n = 66), the rate of excellent response was higher in low-risk patients (80.0%) than in intermediate-risk patients (46.4%) (p = 0.08). Moreover, all patients with initial indeterminate response had an excellent response at the last follow-up visit. ATA risk classes were independently associated with long-term outcome in each subgroup of patients classified dynamically after initial therapy and the overall prognostic performance, defined via ROC curve analysis, of response to initial therapy integrated with the ATA risk system (AUC: 0.89; 95% CI: 0.86-0.92) was significantly higher compared to the ATA risk stratification (AUC 0.69; 95% CI: 0.65-0.74, p < 0.001) or the dynamic risk stratification (DRS) systems alone (AUC: 0.86 95% CI: 0.82-0.90, p = 0.007).

CONCLUSIONS

This study of a large cohort of PTC patients showed that the initial ATA risk criteria may be useful for improving the risk-adapted management of PTC patients based on the response to initial therapy.

Predictive value and dynamic risk stratification of high sensitive basal or stimulated thyroglobulin assay in a long-term thyroid carcinoma cohort

PURPOSE

To evaluate the predictive value of the rhTSH thyroglobulin stimulation test (rhTSH-Tg) compared to basal high-sensitive thyroglobulin (hs-Tg) under TSH suppressive therapy at 12 months after the completion of initial treatment to predict the long-term response and Dynamic Risk Stratification (DRS) at the last follow-up visit in a long-term DTC cohort.

METHODS

Prospective study in 114 DTC patients (77.2% women, mean age 46.4 ± 14.1 years old, median/IQR evolution 6.7[3.1-8.0] years) from 2013 to 2020 undergoing total thyroidectomy and radioiodine ablation in whom hs-Tg and rhTSH-Tg was performed 12 months after completing initial treatment. Pearson correlation, receiving operating characteristics (ROC) and DRS at initial and last follow-up visit were analyzed.

RESULTS

hs-Tg and rhTSH-Tg show a strong positive linear correlation (r = 0.864, p < 0.001). The diagnostic performance of initial hs-Tg and rhTSH-Tg levels were evaluated via ROC-AUC as a predictor of excellent response (ER) in the last follow-up visit. Hs-Tg showed a better AUC (0.969, 95%CI = 0.941-0.997) than rhTSH-Tg (0.944, 95%IC = 0.905-0.984; p < 0.001). The hs-Tg and rhTSH-Tg cutoff point of highest sensitivity (S) and specificity (E) was 0.110 and 0.815 ng/dl, respectively. Hs-Tg showed a higher diagnostic accuracy than rhTSH-Tg (S = 100% vs 96.8%, E = 84.3% vs 84.3%, NPV = 100% vs 98.6%, PPV = 70.5% vs 69.7%; p < 0.05). The DRS based on initial hs-Tg showed better ability to predict ER (93.3% vs 86.7%) and biochemical incomplete response (53.3%vs13.3%) in the last follow-up visit compared to rhTSH-Tg.

CONCLUSIONS

Both initial hs-Th and rhTSH-Tg were good predictors of long-term ER. In patients with hs-Tg, the rhTSH-test did not provide relevant prognosis information. An ER after initial treatment was associated with a very high NPV at subsequent follow-up.

Temporal Evolution and Prognostic Role of Indeterminate Response Sub-Groups in Patients with Differentiated Thyroid Cancer after Initial Therapy with Radioiodine

The clinical outcome of patients affected by Differentiated Thyroid Carcinoma (DTC) and an indeterminate response (IR) after initial therapy is not yet clear. IR includes three different sub-groups of patients: (1) IRTg+ group: Detectable thyroglobulin (Tg), regardless of antithyroglobulin antibodies (TgAb) presence or imaging studies; (2) IRTgAb+ group: Positive TgAb, regardless of Tg levels and nonspecific imaging findings; (3) IRImaging+ group: Nonspecific findings on neck ultrasonography or faint uptake in the thyroid bed on the whole-body scan, negative TgAb, and undetectable Tg. The main aim of this retrospective study was to investigate the dynamic evolution and prognostic role of these patients. From January 2010 to December 2017, 2176 patients who received radioiodine for DTC after total thyroidectomy were included. Two-hundred-eighty-eight patients had IR one year after therapy (187 TgAb+, 76 Tg+, 25 imaging+). After two years, 110 patients (38%) were reclassified as an excellent response and 5 (2%) as an incomplete response; after five years, 221 (77%) achieved an excellent response and 11 (4%) showed an incomplete response. One-year stimulated Tg and nodal disease at diagnosis may predict the final status of the disease. Progression-free survival was significantly shorter in IRTg+ than in IRTgAb+ and IRimaging+ groups. Considering Tg+ patients, a threshold of 3.3 ng/mL is best to predict prognosis.

Risk Reassessment of Differentiated Thyroid Cancer in Ahvaz, Iran: A Cross-sectional Retrospective Study

BACKGROUND

Accurate evaluation of response to treatment in differentiated thyroid cancer (DTC) is the sine qua non of preventing over-treatment in low-risk patients and implementing appropriate interventions in high-risk individuals.

OBJECTIVES

This study aimed to assess the response to therapy in DTC patients based on dynamic stratification method.

METHODS

In this cross-sectional study, 154 medical records of subjects with DTC (with at least 6 months after total thyroidectomy) and referred to endocrinology clinics in Ahvaz, Iran, from April 2020 to May 2021 were examined. Patients were stratified according to a dynamic risk stratification system (informed by their specific clinical, histopathological, and ultrasonography findings, and other diagnostic imagines) into four groups: Excellent response (ER), indeterminate response (IR), biochemical incomplete response (BIR), and structural incomplete response (SIR).

RESULTS

For a mean follow-up period of 28.59 months, excellent response to treatment was observed in 92 patients (59.7%), indeterminate response to treatment was found in 32 patients (20.8%), biochemical incomplete response was detected in 2 patients (1.3%), and structural incomplete response was seen in 28 patients (18.2%). In the group with low risk of recurrence, ER and IR were observed in 79.2% and 15.6% of the patients, respectively (P < 0.0001). In the group with an intermediate risk of recurrence, ER was found in 32% of the patients, while IR and SIR + BIR were seen in 34% and 34% of the patients, respectively (P < 0.0001). No cases of ER or IR were observed in the group with high risk (P = 0.001).

CONCLUSIONS

In sum, response to treatment significantly varied based on dynamic risk stratification, with ER being highest in the low-risk group, less likely in moderate risk group, and undetected in the high-risk group.

Incomplete response to therapy in intermediate- and high-risk thyroid cancer

CONTEXT

The American Thyroid Association (ATA) risk stratification system predicts risk of recurrence of differentiated thyroid cancer (DTC). Although the majority of patients achieve an excellent response, patients with intermediate- or high-risk DTC are at a significant risk of developing incomplete responses. We undertook this work to understand the factors associated with development of biochemically or structurally incomplete response in these two risk subgroups of DTC.

PATIENTS AND METHODS

We retrospectively reviewed 287 consecutive patients with intermediate- (213 patients) or high-risk (74 patients) DTC. All patients underwent total thyroidectomy with (223 patients) or without (64 patients) lymph node dissection and 94% of them received at least one dose of I-131ablation/therapy. Univariate and multivariate analysis and Kaplan Meier analysis were used to compare patients who achieved an excellent response with those who continued to have biochemically or structurally incomplete responses.

RESULTS

In univariate and multivariate analyses, age (P 0.002, Odds ratio 4.8, 95% CI: 1.8-12.9), tumor size (P 0.027, Odds ratio 1.30, 95% CI: 1.03-1.64) and distant metastases (P &lt; 0.0001, Odds ratio 44.6, 95% CI: 10.7-184.5) were significantly associated with the risk of developing biochemically or structurally incomplete statuses. Patients ≥ 55 years, tumors &gt; 2.5 cm and presence of distant metastasis were associated with higher risk of incomplete response and death from DTC. However, when this analysis was performed on intermediate and high-risk groups separately, only age was consistently associated with risk of biochemically or structurally incomplete response in either and both groups.

CONCLUSION

Age is a strong predictor of biochemically and structurally incomplete responses in patients with intermediate and high-risk DTC.

The Initial ATA Risk Classification, but Not the AJCC/TNM Stage, Predicts the Persistence or Relapse of Differentiated Thyroid Cancer in Long-Term Surveillance

Background: The American Joint Commission on Cancer on Tumor Node Metastasis (AJCC/TNM) staging system provides adequate information on the risk of differentiated thyroid cancer (DTC)-specific mortality in totally thyroidectomized patients, but its role in predicting persistence and relapse of disease is uncertain. The relatively new 2015 American Thyroid Association (ATA) guidelines recommend stratifying patients at the time of DTC diagnosis with its own risk classification system, in order to identify those at high risk of residual or recurrent morbidity who may benefit from post-operative radioiodine (RAI) administration and/or need additional work-up. Methods: To verify the prevalence proportion of persistence or relapse of disease, a consecutive cohort of 152 patients with a diagnosis of DTC, subjected to total thyroidectomy (+/− post-operative RAI administration as per guidelines indication) and to neck ultrasonography (US), as well as biochemical surveillance for a minimum of 2 years at the Endocrinology Unit of Mater-Domini Hospital (Catanzaro, Italy), was enrolled. The prognostic role of the AJCC/TNM stage and ATA risk classification system was analyzed by logistic regression. Results: At a mean of 9 years after surgical treatment, DTC was found to persist or relapse in 19 (12.5%) participants. The initial risk for these outcomes, based on the ATA classification, was mostly low (53.9%) or intermediate (39.5%). AJCC/TNM stages were predominantly stage I or stage II. Despite a small representation in this cohort, high-risk patients according to the ATA classification had 8-fold higher odds of persistence or relapse of disease than those of low-risk participants, while controlling for potential risk modifiers, including age at DTC diagnosis, male gender, and post-operative RAI administration (p = 0.008). In contrast, the AJCC/TNM stage was not associated with the disease status at the last follow-up visit (p = 0.068 for the 7th Edition; p = 0.165 for the 8th Edition). Furthermore, low-risk participants subjected to post-operative RAI administration had the same probability of persistence or relapse of DTC when compared to those who had undergone total thyroidectomy only. Conclusions: There is a need for the endocrine community to revise the current work-up of DTC. The initial ATA risk classification is a reliable tool for predicting the persistence or relapse of disease in long-term surveillance.

Natural history, predictive factors of apparent disease (structural or biochemical) and spontaneous excellent response in patients with papillary thyroid carcinoma and indeterminate response to initial therapy with radioiodine

BACKGROUND

About 20% of patients with papillary thyroid carcinoma (PTC) submitted to total thyroidectomy followed by radioactive iodine (RAI) exhibit an indeterminate response to therapy. The aim was to evaluate the natural history, predictive factors of apparent disease (structural or biochemical), and spontaneous excellent response in patients with PTC and an initial indeterminate response to RAI therapy defined based on unstimulated Tg (u-Tg).

METHODS

We evaluated 164 patients who were initially treated with total thyroidectomy and RAI and who had an indeterminate response to therapy (u-Tg between 0.2 and 1 ng/ml, undetectable anti-Tg antibodies [TgAb], and neck ultrasonography [US] without anomalies). None of the patients received empirical therapy with RAI. The patients were followed up for 24 to 144 months (median 72 months).

RESULTS

Apparent disease occurred in 16 patients (9.7%), including 13 with structural disease and 3 with u-Tg elevation > 1 ng/ml, but no tumor was detected by the imaging methods (biochemical disease). A higher frequency of disease was observed in patients with >3 lymph node metastases (LNM) and initial u-Tg >0.35 ng/ml. The frequency was only 2% among patients with ≤3 LNM and u-Tg ≤0.35 ng/ml and 9.7% among patients with > 3 LNM or u-Tg >0.35 ng/ml, while the frequency was 27% in patients with >3 LNM and u-Tg >0.35 ng/ml. In the absence of any additional therapy, u-Tg was <0.2 ng/ml (excellent response) in the last assessment in 70 patients (42.7%). Only initial u-Tg was associated with a higher probability of spontaneously achieving an excellent response: 40/72 patients (55.5%) with u-Tg ≤0.35 ng/ml versus 30/92 patients (32.6%) with u-Tg >0.35 ng/ml.

CONCLUSIONS

A minority of patients with PTC and an initial indeterminate response to RAI defined based on u-Tg develop apparent disease (structural or biochemical) and many spontaneously achieve an excellent response. The risk of disease can be refined based on parameters such as the extent of lymph node involvement and initial Tg concentration.

Differentiated Thyroid Cancer with Biochemical Incomplete Response: Clinico-Pathological Characteristics and Long Term Disease Outcomes

Simple Summary

Biochemical incomplete response (BIR) is defined as elevated thyroglobulin or rising thyroglobulin antibodies following treatment without structural evidence of disease at 1–2 years after initial treatment. The long-term outcome of such patients is still poorly characterized, with some progressing to structural disease, while others maintain BIR for decades or revert to non-evidence of disease (NED). In this study, we aimed to identify factors that could predict any of the above possible outcomes. In our cohort of 83 BIR patients with a mean follow-up of 12 years, 41% progressed to structural disease. Of them, 11.8% remained BIR, and 38.2% reverted to NED.

Abstract

Although most patients with differentiated thyroid cancer (DTC) and biochemical incomplete response (BIR) follow a good clinical outcome, progression to structural disease may occur in 8–17% of patients. We aimed to identify factors that could predict the long-term outcomes of BIR patients. To this end, we conducted a retrospective review study of 1049 charts from our Differential Thyroid Cancer registry of patients who were initially treated with total thyroidectomy between 1962 and 2019. BIR was defined as suppressed thyroglobulin (Tg) > 1 ng/mL, stimulated Tg > 10 ng/mL or rising anti-Tg antibodies, who did not have structural evidence of disease, and who were assessed 12–24 months after initial treatment. We found 83 patients (7.9%) matching the definition of BIR. During a mean follow-up of 12 ± 6.6 years, 49 (59%) patients remained in a state of BIR or reverted to no evidence of disease, while 34 (41%) progressed to structural disease. At the last follow-up, three cases (3.6%) were recorded as disease-related death. The American Thyroid Association (ATA) Initial Risk Stratification system and/or AJCC/TNM (8th ed.) staging system at diagnosis predicted the shift from BIR to structural disease, irrespective of their postoperative Tg levels. We conclude that albeit 41% of BIR patients may shift to structural disease, and most have a rather indolent disease. Specific new individual data enable the Response to Therapy reclassification to become a dynamic system to allow for the better management of BIR patients in the long term.