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Purpose: The aim of this study was evaluate biochemical incomplete response (BIR) in Middle Eastern differentiated thyroid cancer (DTC), identify factors that could predict BIR before radioactive iodine (RAI) ablation and to investigate the long-term clinical outcome of DTC patient exhibiting BIR to initial therapy. Methods: We retrospectively evaluated 1286 DTCs from Middle Eastern ethnicity who underwent total thyroidectomy and RAI therapy. Demograpic and clinico-pathological factors predicting BIR were evaluated. The outcome of these patients was analyzed using primary outcome of structural disease and disease-free survival (DFS). Results: With a median follow-up of 10 years, 266 (20.7%) patients had BIR. High pre-ablation stimulated thyroglobulin (presTg), presence of lymph node metastasis, male gender and delayed initial RAI therapy (≥3 months) after thyroidectomy were significant independent predictors of BIR. Upon evaluating long-term clinical outcomes in 266 patients with BIR, we found 36.8% of patients developed structural disease. Male sex (OR = 1.56; 95% CI = 1.05–2.30; p = 0.0272) and increasing Tg after initial therapy (OR = 4.25; 95% CI = 1.93–10.82; p = 0.0001) were independent risk factors for structural disease in patients with BIR. DFS was significantly worse if both these risk factors existed concomitantly (p < 0.0001). Conclusion: To achieve the fair efficacy of RAI therapy, early prediction of BIR before RAI ablation is desirable. Our finding of the clinico-pathological factors (high presTg level, LNM, delayed RAI therapy and male gender) could serve as easy and robust early predictors of BIR. In addition, DTC patients exhibiting BIR had a high risk of structural disease and hence personalized management approach would be preferable for BIR patients to ensure best clinical outcome. [ABSTRACT FROM AUTHOR]

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.

Context: The clinical response after surgery is a determinant in the management of patients with medullary thyroid carcinoma (MTC). In case of excellent or structural incomplete response, the follow-up strategies are well designed. Conversely, in case of biochemical incomplete response (BiR) the management is not clearly defined. Objective: This work aimed to evaluate the overall and per-site prevalence of structural disease detection in sporadic MTC patients with BiR and to assess the predictive value of various clinical, biochemical, and genetic features. Methods: We evaluated data of 599 consecutive patients surgically treated for sporadic MTC (2000-2018) and followed-up at the endocrine unit of the University Hospital of Pisa. Results: After a median of 5 months from surgery, 145 of 599 (24.2%) patients were classified as BiR. Structural disease was detected in 64 of 145 (44.1%), after a median time of 3.3 years. In 73.6%, structural disease was detected at a single site, prevalently cervical lymph nodes. Among several others, at the time of first evaluation after surgery, only basal calcitonin (bCTN) and stage IVa/b were independent predictive factors. Also, structural disease was more frequent in patients with shorter CTN doubling time and somatic RET mutation. Conclusion: In sporadic MTC patients with BiR, the risk of detection of structural disease was about 50% at 10 years. Higher bCTN levels and staging predicted the risk of detecting structural disease. According to these findings, stricter follow-up should be reserved for MTC with BiR and elevated values of bCTN and to those with an advanced stage. Long follow-up should be considered for all BiR patients since 50% of them develop structural disease within 10 years. [ABSTRACT FROM AUTHOR]

Background and purpose: The prognosis of differentiated thyroid cancer (DTC) patients with suspicious high thyroglobulin (Tg) concentration and without explicit structural lesions varies from each other, hence the clinical treatment decisions including 131I therapy remain controversial. This study aimed to explore the effects of 131I treatment and the therapeutic dose on the clinical outcome of these patients. Methods: The study included 138 DTC patients treated in Department of Nuclear Medicine, Peking Union Medical College Hospital from 2007 to 2021, who had undergone total thyroidectomy and subsequent 131I therapy. All patients were divided into 3 groups as low dose (dose=1.11 GBq), medium dose (1.11 GBq

Objective: The application of radiofrequency ablation (RFA) for recurrent thyroid cancer has been demonstrated to effectively manage lesions at critical locations, such as abutting the trachea, with limited complications. Comprehensive investigation of both biochemical (B) and structural (S) change after RFA remains limited. We herein present the first single-center experience of RFA for the treatment of locoregional recurrent thyroid cancer in Taiwan. Design: 23 patients were enrolled, and the treatment responses after RFA were divided into four groups (E, S(+), B(+), and SB(+)), and then compared. The RFA technique, follow-up strategy, changes in pre-and post-operative status, and complications are presented. The volume reduction rate at 1, 3, and 6 months, and the differing responses between lesions abutting/not abutting the trachea are also discussed. Results: In patients with pre-RFA structural and biochemical incomplete (SB(+)) status, presenting with lesion with an initial maximum diameter of >3.2cm, a higher rate of structural incomplete status at the 6-month follow-up was noted in ROC analysis, with a sensitivity of 57% and specificity of 91%. Favorable structural remission after RFA was noted, and 60.9% of patients achieved biochemical complete status. No significant correlation was noted between the trachea-abutted lesion number and complete remission (p= 0.474). No significant difference in RFA efficacy was noted between the lesions abutting/not abutting the trachea. Conclusions: This retrospective study reveals that RFA can achieve both structural and biochemical improvements for locoregionally recurrent thyroid cancer, with a low complication rate. Nearly half of the patients achieved an excellent response after RFA, while a favorable treatment response can be achieved despite the lesion abutting the trachea, with a mean VRR of 84.74%. [ABSTRACT FROM AUTHOR]

Seung Taek Lim,1 Ye Won Jeon,1 Hongki Gwak,1 Ja Seong Bae,2 Young Jin Suh1 1Division of Breast & Thyroid Surgical Oncology, Department of Surgery, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea; 2Division of Thyroid Surgical Oncology, Department of Surgery, Seoul St. Mary’s Hospital, Catholic University of Korea College of Medicine, Seoul, KoreaCorrespondence: Young Jin SuhDivision of Breast & Thyroid Surgical Oncology, Department of Surgery, St. Vincent’s Hospital, College of Medicine, The Catholic University of Korea, Suwon, KoreaTel +82-31-249-8169Fax +82-31-247-5347Email yjsuh@catholic.ac.krPurpose: To develop a nomogram for predicting biochemical incomplete response (BIR) in the dynamic risk stratification (DRS) of papillary thyroid carcinoma (PTC) patients without structural recurrence, and to investigate its validity.Patients and Methods: Overall, 1705 (1005 and 700 in the training and validation cohorts, respectively) PTC patients treated with total thyroidectomy without structural recurrence were included. multivariate logistic regression analyses were performed to determine the significant predictors of BIR in the training cohort. A nomogram was subsequently constructed for BIR risk prediction. Assessments for the predictive accuracy, discrimination, and calibration of the nomogram were performed. Subsequently, internal and external validations were conducted.Results: In the multivariate analysis, age, sex, lymph node metastasis site, extrathyroidal extension, and lymphovascular invasion showed significant predictive value; using these predictive factors and tumor size, a nomogram for BIR risk prediction was constructed. In the training cohort, the nomogram showed good predictive performance and discrimination in the receiver operating characteristic (ROC) curve analysis, with an area under the curve (AUC) of 0.765. In internal validation, the bootstrap-corrected AUC was 0.76. The calibration plot showed good agreement between the predicted and actual observation. The Hosmer–Lemeshow (HL) test did not suggest a lack of fit (p=0.1613). In the external validation, the AUC was 0.828 in the ROC curve analysis; the calibration plot showed good quality, and the HL test did not suggest a lack of fit (p=0.2161).Conclusion: The constructed nomogram may effectively predict the risk of BIR in DRS in PTC patients without structural recurrence.Level of Evidence: Level 4.Keywords: papillary thyroid carcinoma, dynamic risk stratification, nomogram, biochemical incomplete response

Background and purpose: The prognosis of differentiated thyroid cancer (DTC) patients with suspicious high thyroglobulin (Tg) concentration and without explicit structural lesions varies from each other, hence the clinical treatment decisions including 131I therapy remain controversial. This study aimed to explore the effects of 131I treatment and the therapeutic dose on the clinical outcome of these patients. Methods: The study included 138 DTC patients treated in Department of Nuclear Medicine, Peking Union Medical College Hospital from 2007 to 2021, who had undergone total thyroidectomy and subsequent 131I therapy. All patients were divided into 3 groups as low dose (dose=1.11 GBq), medium dose (1.11 GBq＜dose≤3.70 GBq) and high dose (3.70 GBq＜dose≤7.40 GBq) according to the dose of 131I therapy. We compared the short-term and end-of period response to therapy among these three groups, and further observed the clinical outcome of patients with biochemical incomplete response (BIR) after initial treatment. The receiver operating characteristic (ROC) curve was employed to evaluate the predictive value of stimulated Tg (sTg) levels in patients with structural incomplete response (SIR) and distant metastasis. Results: For the short-term response, the rate of excellent response (ER) was 6.7%, 13.5% and 7.0% in low, medium and high dose group, respectively. The short-term response showed no statistically significant difference among three groups (H=1.02, P=0.60). The end-of-period response among the three groups under routine follow-up also showed no significant difference (H=2.94, P=0.23). No significant difference was observed in the clinical outcome of patients with BIR after routine follow-up and second 131I treatment (U=324.5, P=0.15). The diagnostic critical point (DCP) of sTg to predict SIR and distant metastasis was 27.5 and 61.7 ng/mL, respectively. Conclusion: DTC patients with suspicious high Tg concentration has high recurrence risk, taking 27.5 ng/mL as the cut-off of sTg is helpful to identify the patients with high recurrence risk early. 131I treatment is helpful for these patients to achieve ER as soon as possible. However, highdose 131I did not have greater benefits on the prognosis of these patients. Second 131I treatment showed no further benefit for BIR patients. [ABSTRACT FROM AUTHOR]

Objective: Little is known regarding parameters predicting persistence/recurrence for differentiated thyroid cancer (DTC) patients exhibiting biochemical incomplete response (BIR) to initial therapy. High post-ablation stimulated thyroglobulin (ps-Tg) levels have undetermined prognostic significance in DTC patients with BIR. The goal of this bi-center study was to systemically assess the prognosis of DTC patients with BIR in relation to ps-Tg levels and to establish the determinants of clinical outcomes. Design and methods: The retrospective study of consecutive 81 DTC patients from two tertiary centers who were classified as BIR after total thyroidectomy and radioiodine ablation between January 2010 to December 2019 were analyzed. BIR was defined as ps-Tg > 10 ng/mL measured under thyroid hormone withdrawal at 9–12 months followed by radioiodine ablation, negative anti-Tg antibodies, and no structural evidence of disease. Multivariable regression models were used to evaluate potential risk factors associated with clinical outcomes. Results: With a median follow-up of 5.4 years, 28 patients (34.6%) showed no evidence of disease and 50 patients (61.7%) were of a biochemical persistent status at the time of final follow-up. Conversely, 3 patients (3.7%) developed structural evidence of disease. Ps-Tg of 20.2 ng/mL or greater displayed the high positive predictive value (81%) for disease persistence/recurrence. Multivariate analysis revealed that only a high ps-Tg level (>20.2 ng/mL) was an independent risk factor for persistent/recurrent disease (odds ratio = 5.6; p < 0.001). Conclusion: The ps-Tg (>20.2 ng/mL) was a valuable predictor of disease persistence/recurrence in DTC patients with BIR. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the long-term clinical outcomes of papillary thyroid carcinoma (PTC) patients exhibiting biochemical incomplete response (BIR) to initial therapy. Methods: We evaluated 102 patients with PTC showing a BIR during the first 12–24 months after total thyroidectomy and radioactive iodine therapy. Patients were divided into three groups according to changes in stimulated thyroglobulin (Tg) and anti-Tg antibody (TgAb) levels: the increasing TgAb group (n = 19, 18.6%), the decreasing Tg group (n = 58, 56.9%), and the increasing Tg group (n = 25, 24.5%). Results: With a median follow-up of 12 years, 43 (42%) patients had structural persistent disease as follows: 36 (84%) at regional sites and 7 (16%) at distant sites. The rate of structural persistent disease was significantly different between groups, with 21%, 41%, and 60% in the increasing TgAb, decreasing Tg, and increasing Tg groups, respectively (P = 0.012). Among patients without structural persistent disease, only 19 (18.6%) showed no evidence of disease and 40 (39.2%) were of a biochemical persistent status at the time of final follow-up. Increasing Tg after initial therapy was a significant risk factor for structural persistent disease in patients with BIR (HR, 4.16; 95% confidence interval (CI): 1.38–12.54, P = 0.011). Conclusions: PTC patients with BIR showed a high rate of structural persistent disease and Tg change after initial therapy is the most important prognostic factor for determining clinical outcomes of these patients. [ABSTRACT FROM AUTHOR]

Aim: The aim of the study is to evaluate the value of thyroid-stimulating hormone (TSH)-stimulated thyroglobulin (sTg) measurements by the end of the 1st-year postablation in differentiated thyroid cancer (DTC) patients with biochemical non complete response (indeterminate and incomplete response). Patients and Methods: One hundred patients with DTC underwent near-total thyroidectomy and radioactive remnant ablation by iodine-131 (I131) with regular follow-up every 6 months during the first 2 years and at 6–12-month intervals thereafter by I131 whole-body scan (WBS), neck ultrasound, and sTg measurement in the hypothyroid state (TSH >30 mU/L). Patients were divided according to the imaging findings and sTg level into three groups: excellent response (ER) – no evidence of disease by imaging and sTg <1 ng/mL, indeterminate or acceptable response (AR) – nonspecific findings on imaging studies and sTg < 10 ng/mL, and incomplete response (IR) – patients with incomplete structural and/or incomplete biochemical response (sTg > 10 ng/mL). Results: The follow-up at 6-month postablation showed ER in 3 (3%) patients, AR in 29 (29%) patients, and IR in 68 (68%) patients. The second follow-up at 9–12-month postablation showed dramatic biochemical response with ER, indeterminate, and IR in 50 (50%), 34 (34%), and 16 (16%) patients, respectively, and 14 (14%) patient had structural recurrence. This change is highly statistically significant (P = 0.00). In the last follow-up (ranges from 3 to 10 years), 53 (55.8%) patients achieved ER, 42 (44.2%) AR and no patient with non complete response. The change in patients with IR between the second and the last follow-up is also statistically significant (P = 0.001). Conclusion: sTg measurement by the end of the 1st year is more reliable in the follow-up of patients with DTC and biochemical non complete response and considered significant predictor of disease-free status. Patients with biochemical IR still have the chance to achieve ER or AR by the passage of time without additional therapies. [ABSTRACT FROM AUTHOR]

• LNR was independently associated with postoperative Tg levels. • Patients with a high LNR were more likely to have biochemical incomplete response. • The mean LNR in the central neck was 0.22. • The mean LNR in the lateral neck was 0.06. • Twenty patients (16.9%) had postablative uTg ≥ 1 ng/mL. To investigate the impact of the lymph node ratio (LNR) on postoperative thyroglobulin (Tg) levels in patients with papillary thyroid carcinoma (PTC). This was a retrospective, cohort study. The association between clinicopathological variables and postoperative unstimulated Tg (uTg) levels, preablative-stimulated Tg (sTg) levels, and postablative unstimulated Tg levels was analysed. A total of 300 patients with PTC were identified. Multivariate logistic analysis showed that M classification (odds ratio [OR], 2.33; 95% confidence interval [CI], 1.62–3.34), and postoperative thyroid-stimulating hormone levels (OR, 1.01; 95% CI, 1.01–1.02) were independently associated with postoperative uTg levels. One hundred and sixteen patients underwent radioactive iodine (RAI) therapy. Multivariate analysis showed that LNR in the central neck (OR, 1.24; 95% CI, 1.02–1.51), LNR in the lateral neck (OR, 1.73; 95% CI, 1.09–2.77), RAI dose (OR, 1.43; 95% CI, 1.21–1.69), and M classification (OR, 1.79; 95% CI, 1.22–2.61) were independently associated with preablative sTg levels. Tumour size (OR, 1.01; 95% CI, 1.00–1.01), LNR in the central neck (OR, 1.28; 95% CI, 1.08–1.51), LNR in the lateral neck (OR, 1.66; 95% CI, 1.10–2.49), RAI dose (OR, 1.54; 95% CI, 1.34–1.79), and M classification (OR, 1.56; 95% CI, 1.12–2.19) were also independently associated with postablative uTg levels. LNR was independently associated with postoperative Tg levels in patients with PTC. Patients with high LNR were more likely to have incomplete biochemical responses after surgery. [ABSTRACT FROM AUTHOR]

Introduction: Patients with incomplete response to initial therapy of thyroid cancer can be managed with ongoing observation or potentially additional therapies. Our aim was to assess the effect of a second radioactive iodine treatment (RAIT) and its relationship with causes and clinical variables., Material and Methods: Patients undergoing a second RAIT for biochemical or structural incomplete response to initial therapy of DTC were retrospectively included (n=120). They were categorised based on the American Thyroid Association (ATA) classification of response to initial therapy. Patients were reclassified in the following 6-18 months after second RAIT based on imaging findings and measurements of thyroglobulin and antithyroglobulin antibody levels. The associations of a downgrading of response category and progression-free survival (PFS), and the related variables, were evaluated., Results: Sixty-six patients (55%) had a downgrading on ATA response category after second RAIT. A significant interdependence of causes for second RAIT and outcomes was found (χ 2 =29.400, p=0.001), with patients with neck reoperation showing a higher rate of indeterminate or excellent responses. A significant association between ATA response to second RAIT and absence of structural progression was found (χ 2 =44.914, p<0.001), with less structural progression in patients with downgrading on ATA response (χ 2 =30.914, p<0.001). There was also significant interdependence to some clinical variables, such as AJCC stage (χ 2 =8.460, p=0.015), ATA risk classification (χ 2 =10.694, p=0.005) and initial N stage (χ 2 =8.485, p=0.004)., Conclusions: In selected cases, a second RAIT could lead to more robust responses with a potential improvement in prognosis in patients with incomplete response to initial DTC treatment., (Copyright © 2023 SEEN and SED. Published by Elsevier España, S.L.U. All rights reserved.)

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.

Objective: The application of radiofrequency ablation (RFA) for recurrent thyroid cancer has been demonstrated to effectively manage lesions at critical locations, such as abutting the trachea, with limited complications. Comprehensive investigation of both biochemical (B) and structural (S) change after RFA remains limited. We herein present the first single-center experience of RFA for the treatment of locoregional recurrent thyroid cancer in Taiwan., Design: 23 patients were enrolled, and the treatment responses after RFA were divided into four groups ( E , S(+) , B(+) , and SB(+) ), and then compared. The RFA technique, follow-up strategy, changes in pre-and post-operative status, and complications are presented. The volume reduction rate at 1, 3, and 6 months, and the differing responses between lesions abutting/not abutting the trachea are also discussed., Results: In patients with pre-RFA structural and biochemical incomplete ( SB(+) ) status, presenting with lesion with an initial maximum diameter of >3.2cm, a higher rate of structural incomplete status at the 6-month follow-up was noted in ROC analysis, with a sensitivity of 57% and specificity of 91%. Favorable structural remission after RFA was noted, and 60.9% of patients achieved biochemical complete status. No significant correlation was noted between the trachea-abutted lesion number and complete remission (p= 0.474). No significant difference in RFA efficacy was noted between the lesions abutting/not abutting the trachea., Conclusions: This retrospective study reveals that RFA can achieve both structural and biochemical improvements for locoregionally recurrent thyroid cancer, with a low complication rate. Nearly half of the patients achieved an excellent response after RFA, while a favorable treatment response can be achieved despite the lesion abutting the trachea, with a mean VRR of 84.74%., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Chen, Chou, Chang, Chiang, Lim, Chi, Luo and Lin.)

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. 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. [ABSTRACT FROM AUTHOR]

Objectives: To assess the value of 18 F-FDG-PET/CT for detecting recurrent/persistent disease in patients with biochemical incomplete (BIR) or indeterminate response (IR) and to assess the impact of 18 F-FDG-PET/CT on the therapeutic management of these patients., Methods: The study included patients with BIR, in whom 18 F-FDG PET/CT was used within the diagnostic algorithm from our database. Patients with IR referred to our hospital with the 18 F-FDG PET/CT already performed were also enrolled. All patients had neck ultrasonography with no structural changes. A change in therapeutic approach was defined as repeat surgery; administration of external beam radiotherapy; and/or the start of systemic therapy., Results: Sixty patients (85% women) aged 18-86 years were enrolled in this retrospective study. Of these, 75% had BIR and 25% IR. Increased FDG uptake suggesting locoregional lesions was seen in 40% of patients. Sensitivity, specificity, and diagnostic accuracy of 18 F-FDG PET/CT to detect local disease were 95%, 87.5% and 90% respectively. The therapeutic approach was modified in 50% of patients with locoregional lesions., Conclusions: Our study confirmed that 18 F-FDG-PET/CT is a useful tool for detecting locoregional recurrence in thyroid cancer patients with BIR or IR with conflicting findings in standard diagnostic procedures. In 50% of patients with locoregional lesions, there was an immediate change in the treatment approach., (Copyright © 2020 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.)