Delayed initial radioiodine therapy related to incomplete response in low- to intermediate-risk differentiated thyroid cancer

Predicting factors and clinical outcome of biochemical incomplete response in middle eastern differentiated thyroid carcinoma

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.

Analysis of delayed initial radioactive iodine therapy and clinical outcomes in papillary thyroid cancer: a two-center retrospective study

BACKGROUND

It remains unclear whether the time interval between total thyroidectomy and radioactive iodine (RAI) therapy influences clinical outcomes in papillary thyroid carcinoma (PTC). This study aims to evaluate the impact of the timing to initiate RAI therapy on the response in PTC patients.

METHODS

We retrospectively included 405 patients who underwent total thyroidectomy and subsequent RAI therapy at two tertiary hospitals in southwest China. Patients were categorized into two groups based on the interval between thyroidectomy and initial RAI therapy, that is, an early group (interval ≤90 days, n  = 317) and a delayed group (interval >90 days, n  = 88). Responses to RAI therapy were classified as excellent, indeterminate, biochemical incomplete, or structural incomplete. Univariate and multivariate analyses were conducted to identify factors associated with a nonexcellent response.

RESULTS

Excellent responses were observed in 77.3% of the early group and 83.0% of the delayed group ( P  = 0.252). No significant impact of RAI therapy timing was also observed across all American Thyroid Association risk classification categories. These findings persisted when patients were analyzed separately according to RAI dose (intermediate-dose group: 3.7 GBq [ n  = 332]; high-activity group: ≥5.5 GBq [ n  = 73]), further subdivided by the timing of RAI therapy. Multivariate analysis identified lymph node dissection, RAI dose, and stimulated thyroglobulin as independent risk factors for excellent response ( P  < 0.05).

CONCLUSION

The timing of initial RAI therapy following surgery did not significantly affect outcomes in patients with PTC.

Advances in the selection and timing of postoperative radioiodine treatment in patients with differentiated thyroid carcinoma

Differentiated thyroid cancer (DTC) is the most common endocrine malignancy. Patients who receive systematic care typically have a better prognosis. RAI treatment plays a key role in eradicating any remaining thyroid lesions in DTC patients, hence decreasing the risk of distant metastases and cancer recurrence. As research continues to advance, RAI treatment is becoming more and more individualized. Because of the excellent prognosis for DTC patients, there is a relatively broad window for RAI treatment, making it easy to overlook when to receive RAI treatment. However, research on this issue can help patients with varying recurrence risk stratification make better decisions about when to begin RAI treatment following surgery, and physicians can schedule patients based on the severity of their disease. This will improve patient prognosis and lessen needless anxiety in addition to helping solve the problems of unjust healthcare resource distribution. In this review, we will mainly discuss the target population of RAI treatment as well as studies that examine the impact of RAI treatment timing on patient outcomes. In an effort to discourage DTC patients and physicians from selecting RAI therapy at random, we also review the possible negative effects of this treatment.

Predicting excellent response to radioiodine in differentiated thyroid cancer using machine learning

Objective

If excellent response (ER) occurs after radioactive iodine (RAI) treatment in patients with differentiated thyroid carcinoma (DTC), the recurrence rate is low. Our study aims to predict ER at 6-24 months after RAI by using machine learning (ML) methods in which clinicopathological parameters are included in patients with DTC without distant metastasis.

Methods

Treatment response of 151 patients with DTC without distant metastasis and who received RAI treatment was determined (ER/nonER). Thyroidectomy ± neck dissection pathology data, laboratory, and imaging findings before and after RAI treatment were introduced to ML models.

Results

After RAI treatment, 118 patients had ER and 33 had nonER. Before RAI treatment, TgAb was positive in 29% of patients with ER and 55% of patients with nonER (p = 0.007). Eight of the ML models predicted ER with high area under the ROC curve (AUC) values (> 0.700). The model with the highest AUC value was extreme gradient boosting (AUC = 0.871), the highest accuracy shown by gradient boosting (81%).

Conclusions

ML models may be used to predict ER in patients with DTC without distant metastasis.

Impact of the COVID-19 Pandemic on Thyroid Cancer Surgery

The COVID-19 pandemic caused major disruptions to healthcare services in 2020, delaying cancer diagnosis and treatment. While early-stage thyroid cancer often progresses slowly, it is crucial to determine whether treatment delays associated with the pandemic have impacted the clinical presentation and management of advanced-stage thyroid cancer. The purpose of our study was to determine the impact of the early COVID-19 pandemic on thyroid cancer presentation and treatment times. Utilizing the National Cancer Database, chi-squared tests and regression analyses were performed to compare patient demographic and clinical characteristics over time for 56,011 patients diagnosed with primary thyroid cancer who were treated at the Commission on Cancer-accredited sites in 2019 and 2020. We found that thyroid cancer diagnoses decreased between 2019 and 2020, with the biggest drop among patients with cT1 disease relative to other T stages. We also found that patients diagnosed with thyroid cancer in 2020 had similar treatment times to patients diagnosed in 2019, as measured by both the time between diagnosis and start of treatment and the time between surgery and start of radioactive iodine therapy. Overall, our study suggests that resources during the pandemic were allocated to patients with advanced thyroid disease, despite a decrease in diagnoses.

Ablation Rates and Long-Term Outcome Following Low-Dose Radioiodine for Differentiated Thyroid Cancer in the West of Scotland: A Retrospective Analysis

OBJECTIVE

Low-dose radioiodine is an accepted means of remnant ablation in patients with low- to intermediate-risk differentiated thyroid cancer (DTC) based on the results of several phase III trials. We evaluated the rate of ablation success and long-term recurrence outcomes in the first 3 years of implementing this practice at our institution.

METHODS

Patients who received 1.1 to 1.2 gigabecquerel (30 millicurie) were identified retrospectively from the radionuclide database, January 1, 2012, to December 31, 2014, inclusive. Successful ablation was defined as Iodine-131uptake <0.1% on diagnostic scan and Tg level <2.0 ng/mL at 6 to 8 months after treatment. Follow-up was conducted annually for 10 years and relapse rates were determined based on the available clinical, radiological, and biochemical information.

RESULTS

We identified 114 patients, 109 of whom had dual response assessment. The median age was 43 years (range, 14 to 80 years). Almost 70% had T1 or T2 tumors, with T3 and T4 tumors recorded in 27% and 2.5% of patients, respectively. Nodal staging was performed in just over 30% and involved lymph nodes were detected in 21% (N1a 8% and N1b 13%). Ablation success based on diagnostic scan alone was 94.7% (108/114), Tg alone 94.7% (108/114), and on both modalities was 90.4% (103/114).

CONCLUSION

Remnant ablation was achieved in >90%, and the corresponding clinical recurrence rate was only 1.8% despite the inclusion of patients with locally advanced disease. Low-dose radioiodine is effective and may be suitable for a proportion of patients with higher-risk DTC.

Impact factors of benefiting from initial 131 I ablation in patients with intermediate-risk differentiated thyroid carcinoma: a study based on a re-evaluation of therapeutic response

OBJECTIVE

This study was carried out to confirm whether patients with intermediate-risk differentiated thyroid cancer (DTC) could benefit from initial 131 I ablation and to identify the factors that impacted the benefit.

METHODS

We retrospectively assessed a cohort of 548 patients with intermediate-risk DTC who were classified into structural incomplete response (SIR), biochemical incomplete response (BIR), indeterminate response (IDR), and excellent response (ER) groups according to the ATA guidelines (version 2015). A downgrade in the classification, such as from initial SIR to final BIR, IDR, or ER, from BIR to IDR or ER, and from initial IDR to final ER, was defined as benefiting from initial 131 I ablation (benefit group). Non-downgraded classification meant non-benefit.

RESULTS

64.78% of patients benefited from the initial 131 I ablation in the final re-evaluation. Gender (OR = 0.038, P  = 0.002), interval time (OR = 0.038, P  = 0.002) and serum ps-Tg (OR = 0.961, P  = 0.001) were independent prognostic factors for benefiting from initial 131 I ablation, with the cutoff value were 5 months and 19.08 ng/ml.

CONCLUSION

Patients with intermediate-risk DTC could benefit from initial 131 I ablation. Female patients with intermediate-risk DTC whose interval time <5 months and ps-Tg <19.08 ng/ml were more likely to benefit. Early 131 I ablation for such patients is beneficial for achieving a complete therapeutic response.

Effect of Waiting Time for Radioactive Iodine Therapy on Outcome in N1 Stage Papillary Thyroid Cancer

CONTEXT

The waiting time for radioactive iodine therapy (WRAIT) after total thyroidectomy (TT) in patients with papillary thyroid cancer (PTC) and lymph node metastases (N1) has not been sufficiently investigated for risk of adverse outcomes.

OBJECTIVE

This work aimed to estimate the effect of WRAIT on the outcomes of disease persistence and recurrence among patients with N1 PTC and investigate factors predictive of delayed radioactive iodine therapy (RAIT).

METHODS

This retrospective cohort study was conducted in a university hospital. A total of 909 patients with N1 PTC were referred for RAIT between 2014 and 2018. WRAIT is the duration between TT and initial RAIT. The optimal WRAIT threshold determined using recursive partitioning analysis was used to define early and delayed RAIT. The primary end point was tumor persistence/recurrence. We compared the outcomes of patients with early and delayed RAIT using inverse probability weighting based on the propensity score.

RESULTS

The WRAIT threshold that optimally differentiated worse long-term remission/excellent response outcomes was greater than 88 days (51% of our cohort; n = 464). WRAIT exceeding 88 days was associated with an augmented risk of disease persistence/recurrence (odds ratio, 2.47; 95% CI, 1.60-3.82) after adjustment. Predictors of delayed RAIT included residence in lower-income areas, reoperation before the initial RAIT, TT at a nonuniversity-affiliated hospital, multifocality, extrathyroidal extension, N1b disease, and pre-RAIT-stimulated thyroglobulin level less than 1 ng/mL.

CONCLUSION

Delayed RAIT beyond 88 days after TT in patients with N1 PTC independently increased the risk of disease persistence/recurrence. Evaluation of the predictive determinants of prolonged WRAIT may help target at-risk patients and facilitate interventions.

Factors Affecting Ablation Success After I-131 Radioactive Iodine Therapy in Low and Intermediate Risk Papillary Thyroid Cancer

The study was to evaluate the effect of radioactive iodine (RAI) treatment application time and clinical, histopathological factors on ablation success in patients with operated papillary thyroid cancer (PTC) in low and intermediate-risk. One hundred sixty-one patients with PTC in the low and intermediate-risk were evaluated. Most patients (89.4%) were in the low-risk, and 10.6% were in the intermediate-risk. When the patients were divided into two groups according to the date of receiving RAI treatment after surgery, those who received early treatment (≤3 months) constituted the majority of the patients (72.7%). Seventeen patients received 1.85 Gigabecquerel (GBq), 119 3.7 GBq, 25 5.55 GBq RAI. Most patients (82%) achieved ablation success after the first RAI treatment. The time interval between surgery and RAI treatment did not affect ablation success. Stimulated Tg level measured on the RAI treatment day was an independent predictive factor for successful ablation (p<0.001). The cut-off value of Tg found to predict ablation failure was 5.86 ng/ml. It was concluded that 5.55 GBq RAI treatment could predict ablation success compared to 1.85 GBq dose (p=0.017). It was concluded that having a T1 tumor may predict treatment success compared to a T2 or T3 tumor (p=0.001, p<0.001, retrospectively). The time interval does not affect ablation success in low and intermediate-risk PTC. The ablation success rate may decrease in patients who receive low-dose RAI and have high Tg levels before treatment. The most crucial factor in achieving ablation success is giving enough doses of RAI to ablate the residual tissue.

The influence of stimulated thyroglobulin and lymphocyte subsets before radioiodine therapy on the therapeutic response in patients with intermediate- and high-risk papillary thyroid carcinoma

The aim of the present study was to investigate the factors influencing the short-term response to the initial radioiodine therapy (RT) course in patients with intermediate- and high-risk papillary thyroid carcinoma (PTC). A total of 182 patients with intermediate- and high-risk PTC who underwent RT in our hospital from March 2018 to October 2020 were retrospectively enrolled. The patients were divided into incomplete response (IR) and nonincomplete response (Non-IR) groups according to the response observed in clinical follow-up within 6-12 months after RT. Univariate and multivariate logistic regression analyses were used to investigate the effects of 15 observed factors on the response to RT. Receiver operating characteristic (ROC) curve analysis was used to determine the value of factors found to be significant in multivariate analyses for predicting an IR. A total of 182 patients with intermediate- and high-risk PTC were analyzed; the percentage of patients with a Non-IR was 61.54% (112/182), and the percentage of patients with an IR was 38.46% (70/182). The CD4+ T-cell percentage (t = 4.757, P = 0.000), CD4/CD8 (z = - 2.632, P = 0.008), stimulated thyroglobulin (sTg) level (z = - 8.273, P = 0.000) and M stage (χ2 = 17.823, P = 0.000) of the two groups were significantly different. Multivariate analysis showed that only the sTg level (OR: 1.116, 95% CI 1.068-1.165, P < 0.001) and CD4+ T-cell percentage (OR: 0.909, 95% CI 0.854-0.968, P = 0.003) were independent factors associated with the therapeutic response to RT. The cutoff sTg level and CD4+ T-cell percentage for predicting an IR were 7.62 μg/L and 40.95%, respectively. The sTg level and CD4+ T-cell percentage were verified to be independent predictive factors of RT response. Higher sTg levels and lower CD4+ T-cell percentages were related to an IR in patients with intermediate- and high-risk PTC.

The prognostic value of post thyroidectomy Tc-99m pertechnetate thyroid scan in patients with differentiated thyroid cancer

AIM

To evaluate the prognostic value of postoperative Tc-99m pertechnetate scanning in patients with differentiated thyroid cancer (DTC).

METHOD

Patients with pathologically proven low or intermediate-risk DTC were enrolled in this study. Postoperative Tc-99m pertechnetate scintigraphy was performed 20 min after IV of 185 MBq of Tc-99m pertechnetate Positive thyroid residual uptake was characterized as higher Tc-99m pertechnetate uptake at the thyroid bed than the surrounding background's activity. A negative residual was considered if there was no definite abnormal radioactivity at the thyroid bed. Follow-up by thyroglobulin, thyroglobulin antibodies (Tg Abs), neck ultrasound (US) and diagnostic I-131 WBS (Dx WBS) were considered the reference standard. Successful ablation outcome was considered if there was free Dx WBS, stimulated serum thyroglobulin < 1 ng/ml with negative Tg Abs, and free US.

RESULT

Two hundred and two patients, mean age; of 38.8 years were retrospectively recruited in this study. Positive residual uptake at the thyroid scan was detected in 131 patients wherea the remaining 71 patients had no detectable uptake. According to the reference standard we encountered 114 and 88 cases with successful ablation and unsuccessful ablation respectively, Tc-99m pertechnetate scanning successfully detected 63 true positive and 46 true negative cases giving 72% sensitivity, 40% specificity, 48% positive predictive value and 56% negative predictive value.

CONCLUSION

In low- and intermediate-risk DTC patients; despite the relatively high sensitivity of postoperative Tc-99m pertechnetate thyroid scan, it has low specificity and low negative predictive value so it cannot be used to predict the ablation outcome.

Delay of initial radioactive iodine therapy beyond 3 months has no effect on clinical responses and overall survival in patients with thyroid carcinoma: A cohort study and a meta-analysis

BACKGROUND

More than a third of thyroid carcinoma (TC) patients require treatment with radioactive iodine (RAI), but the timing of initial RAI therapy after thyroidectomy remains controversial.

METHODS

We included 1224 differentiated thyroid carcinoma (DTC) patients during 2015-2019, divided them into the early (≤3 months) and the delayed (>3 months) groups based on the interval between surgery and the initial RAI. Clinical outcomes were assessed within 6-8 months of treatment with RAI, including excellent response (ER), indeterminate response (IDR), biochemical incomplete (BIR) and structural incomplete response (SIR). Further transformed them into dichotomous outcomes, we therefore introduced the ordered/binary logistic regression to assess the relation of time interval and quaternary/dichotomous outcomes, respectively. Finally, we conducted a meta-analysis for cohort study to investigate the effect of timing of RAI therapy on the prognosis of TC.

RESULTS

Delay RAI therapy beyond 3 months reduced the IR (BIR + SIR) rate in the present cohort study (RR = 0.67, 95% CI: 0.49-91). Following meta-analysis including 38,688 DTC patients confirmed these results (RR = 0.77, 95% CI: 0.66-0.91), further revealed the duration of treatment does not influence OS (pooled RR = 1.05, 95% CI: 0.83-1.33).

CONCLUSION

Delayed initial RAI therapy beyond 3 months but no later than 6 months did not impair the prognosis of TC.

Delayed Initial Radioiodine Adjuvant Therapy Does Affect Biochemical Response in Intermediate- to High-Risk Differentiated Thyroid Cancer

Background

There are no definite recommendations on the optimal time of initiating radioactive iodine (RAI) therapy for differentiated thyroid cancer (DTC) patients in current relevant guidelines. This study aimed to investigate the relationship between the timing of initiating radioiodine adjuvant therapy (RAT) and the clinical outcomes based on dynamic follow-ups and assessments in intermediate- to high-risk DTC patients.

Methods

A total of 206 patients with intermediate- to high-risk DTC receiving RAT of 150 mCi were retrospectively reviewed. According to the time interval (TI: between thyroidectomy and initial RAT), the patients were divided into 2 groups: Group 1: TI < 3 months (n=148), and Group 2: TI ≥ 3 months (n=58). The RAT therapy response was evaluated as excellent response (ER), indeterminate response (IDR), biochemical incomplete response (BIR), structural incomplete response (SIR). The univariate and multivariate analyses were conducted to screen out factors associated with incomplete response (IR= BIR+SIR). Finally, the prognostic nomogram was used to explain IR rates as a valuable tool in clinical practice.

Results

Response to initial RAT was significantly different between 2 groups during dynamic follow-ups (all P<0.05). Group 2 had significantly lower ER rates (37.9 vs 63.5, 52.0 vs 73.9, 64.4 vs 80.3, all P<0.05, respectively) and higher IR rates (39.7 vs 14.9, 36.0 vs 9.7, 12.2 vs 3.9, all P<0.05, respectively) than group 1 during dynamic follow-ups. By univariate and multivariate analyses, prolonged TI (HR: 6.67, 95%CI: 2.241-19.857, P=0.001), soft tissue invasion (HR: 7.35, 95%CI: 1.624-33.296, P=0.010), higher sTg (HR: 7.21, 95%CI: 1.991-26.075, P=0.003) were manifested to be independent risk factors for IR. The nomogram showed that soft tissue invasion, sTg, and TI were the top 3 contributors to the IR.

Conclusions

Early RAT is associated with greater biochemical response but has no impact on SIR. Delayed initial RAT (≥3 months after thyroidectomy) related to IR in intermediate- to high-risk DTC.

Clinical Analysis of the Short-Term Outcome of Papillary Thyroid Micro Carcinoma After 131I Treatment

Purpose

To explore the factors that influence the short-term clinical outcome after the first ¹³¹I treatment of papillary thyroid micro carcinoma (PTMC).

Patients and Methods

From October 2015 to June 2018, patients who were diagnosed with PTMC with lymph node metastasis were analyzed retrospectively, excluding patients with incomplete clinical data, distant metastasis, positive TGAb, TSH<30 mIU/L. The baseline data of sex, age, time from last surgery to first ¹³¹I treatment, tumor pathology information, and biochemical information were collected before admission. All patients included had radioactive iodine (RAI) with 3.70 GBq. The treatment response of patients was evaluated 6–8 months after discharge. By means of univariate and multivariate analysis, including excellent response (ER) and non-excellent response (NER) groups of clinical data, we assessed the impact of ¹³¹I on patients’ outcome. A nomogram model was established based on the above independent risk factors.

Results

A total of 206 patients (59 males and 147 females, mean age 43.4 ± 10.6 years) were included in the study. The median follow-up time was 169.4 ± 10.5 days, including 139 patients in ER group (67.4%) and 67 patients in NER group (32.5%). Four factors including combining Hashimoto’s thyroiditis, pre-ablative Tg levels, UIE levels, and lateral lymph node numbers were statistically different between ER group and NER group with significance at P < 0.05. Further multivariate analysis showed that Hashimoto’s thyroiditis and Ps-Tg levels could be used as independent factors. The model verification showed that the C-index of the modeling set was 0.822, indicating that the nomogram model had a good predicted accuracy.

Conclusion

Our data suggest that coexisting Hashimoto’s thyroiditis and elevated Ps-Tg levels are predictive factors for short-term outcome of thyroid micro papillary carcinoma after ¹³¹I treatment. Also, the nomogram model had a good predicted accuracy.

Analysis of Curative Effect and Influencing Factors of N1 Stage Papillary Thyroid Micro-Carcinoma and Papillary Thyroid Non-Micro Carcinoma After Initial Radioactive Iodine Ablation Therapy

Objective

To compare the efficacy and influencing factors of initial radioactive iodine (RAI) ablation therapy for postoperative N1 stage papillary thyroid micro-carcinoma (PTMC) and papillary thyroid non-micro carcinoma (PTC), and to explore the necessity of RAI for N1 stage PTMC.

Methods

A retrospective analysis of patients with N1 stage papillary thyroid cancer who underwent RAI in our department from January 2018 to June 2019. According to the tumor diameter, papillary thyroid carcinoma was divided into PTMC group (≤ 1.0cm) with 129 patients and PTC group (> 1.0 cm) with 214 patients. According to the 2015 ATA guidelines, the patient’s treatment response was evaluated 6–8 months after discharge from the hospital: excellent response (ER), indeterminate response (IDR), biochemical incomplete response (BIR), and structural incomplete response (SIR). IDR, BIR, and SIR were classified into NER group. Chi-squared test, independent sample t-test, Mann–Whitney U test, and binary logistic regression analysis were used to compare the differences between PTMC and PTC patients.

Results

The ps-Tg of the PTMC group was significantly lower than that of the PTC group (P = 0.001), and the ER ratio of the PTMC group was higher (χ² = 5.445, P < 0.05). The ER ratio of PTMC patients in the N1a group was significantly higher than that of PTC patients (80%, 66.7%, χ² = 4.076, P < 0.05), while the ER ratio of PTMC in the N1b group was not significantly different from that of PTC. Gender, N stage, and ps-Tg were found to be independent factors of RAI treatment response.

Conclusion

The efficacy of the initial RAI of PTMC patients was significantly better than that of PTC patients. There was no significant difference in the efficacy of RAI between males with PTMC, N1b stage, ps-Tg ≥ 5.87ng/mL and PTC patients, which suggested that RAI is necessary for these patients.

Applying postoperative radioiodine therapy before 3 months seems to decrease ablation success in patients with differentiated thyroid carcinoma

OBJECTIVES

Radioiodine can be applied for remnant ablation in low and low to intermediate-risk patients with differentiated thyroid cancer (DTC). A controversy still exists about the application time interval of radioiodine following total thyroidectomy. In this study, we investigated the effect of radioiodine (RAI) therapy timing on the success rates of the ablation.

METHODS

We retrospectively reviewed the data of DTC patients who underwent total thyroidectomy and were treated with radioiodine remnant ablation during 2013-2017. Because the objective of this study was to determine the success of ablation according to the postoperative RAI therapy timing, any patients with a pathologic uptake outside the thyroid bed as well as high-risk patients determined before and at RAI therapy were excluded from the study. Finally, 503 patients with low and low to intermediate-risk groups were included in the study. Successful ablation was defined as no visible focal uptake on the neck on I-131 whole body scan with stimulated thyroglobulin (Tg) level of < 1 ng/mL and a normal or undetectable antithyroglobulin antibody (ATG). The time interval from total thyroidectomy to RAI therapy (titRAI) was calculated as months for each patient.

RESULTS

A total of 115 (22.9%) patients were in the low to intermediate-risk group whereas most of the patients were at the low-risk group according to the American Thyroid Association (ATA) 2015. Successful ablation was observed in 388 (77.1%) patients. The titRAI was ≤ 3 months in 151 (30.0%) patients and > 3 months in 352 (70.0%) patients. The ratio of successful ablation was statistically higher in patients with a titRAI > 3 months (81.2% of patients) than in patients with ≤ 3 months (67.5% of patients) (χ² 11.247, p 0.001). The rate of successful ablation was 20.3% higher in patients treated after 3 months. There was no statistical difference when titRAI cut off was reduced to 2 months (p > 0.5).

CONCLUSION

Investigated the effect of radioiodine therapy initiated before 3 months after total thyroidectomy and it seems to decrease ablation success.

Clinical Outcomes after Early and Delayed Radioiodine Remnant Ablation in Patients with Low-Risk Papillary Thyroid Carcinoma: Propensity Score Matching Analysis

BACKGROUND

The clinical outcomes of delayed radioiodine remnant ablation (RRA) therapy in patients with low-risk papillary thyroid carcinoma (PTC) are unclear. We aimed to evaluate the clinical impact of the interval between total thyroidectomy (TT) and RRA therapy in patients with low-risk PTC.

METHODS

We included 526 patients who underwent TT and RRA for low-risk PTC with a primary tumor size of >1 cm between 2000 and 2012. Patients were divided into the early (<90 days) and the delayed (≥90 days) RRA groups based on the interval between TT and RRA. The results of diagnostic whole-body scan (DxWBS), ongoing risk stratification (ORS; response to therapy), and disease-free survival (DFS) were evaluated before and after propensity score matching (PSM).

RESULTS

Among the 526 patients, 75 (14.3%) patients underwent delayed RRA; they had more cervical lymph node metastasis and received a higher RRA dose than those who underwent early RRA. The median follow-up period was 9.1 years after initial therapy, and the structural recurrence rate was 1.9%. In DxWBS, 60 patients had focal iodine uptake limited in operative bed, with no significant difference between groups. According to ORS, 78%, 20%, 1%, and 1% patients were classified into excellent, indeterminate, biochemical incomplete, and structural incomplete response groups, respectively. There was no significant difference in ORS or DFS between groups before and after PSM.

CONCLUSION

The timing of the first RRA had no clinical impact in patients with low-risk PTC. Thus, the clinical decision for RRA can be determined >3 months after TT considering other prognostic factors.

Lymphocyte-to-monocyte ratio prior to radioiodine ablation in low- and intermediate-risk, papillary thyroid cancer

PURPOSE

We aimed to investigate inflammation indices based on preablation hematological parameter of the lymphocyte-to-monocyte ratio (LMR) to predict the clinical outcome in papillary thyroid cancer (PTC) patients with low- and intermediate-risk stratification.

METHODS

This retrospective study analyzed 772 patients with low- and intermediate-risk PTC who underwent total thyroidectomy followed by radioiodine therapy between July 2005 and July 2009 with a median of 10 years. Kaplan-Meier statistics were used to test differences in recurrence-free survival (RFS) between groups based on the optimal cutoff point of biomarkers identified using receiver operating characteristic curves.

RESULTS

With an optimal cutoff point of 7.05, 215 patients (29.8%) were classified as having low LMR and 557 patients (71.2%) were classified as having high LMR. High LMR was significantly associated with a prolonged RFS (hazard ratio [HR]: 2.048, 95% confidence interval [CI]: 1.062-4.359, p = 0.001). Multivariate analysis showed that low LMR (HR = 2.035, 95% CI: 1.011-4.095, p = 0.012), tumor size over 2 cm (HR = 2.762, 95% CI: 1.303-5.852, p = 0.008), and high preablative simulated thyroglobulin level over 10 ng/ml (HR = 7.826, 95% CI: 2.353-26.033, p < 0.001) were independent prognostic markers for worse RFS in the enrolled PTC patients.

CONCLUSIONS

LMR at the time of radioiodine therapy has comparable predictor for the clinical outcome with both tumor size and preablative simulated thyroglobulin level in low- to intermediate-risk PTC patients.

Preoperative Use of Intravenous Contrast Media Is Associated With Decreased Excellent Response Rates in Intermediate-Risk DTC Patients Who Subsequently Receive Total Thyroidectomy and Low-Dose RAI Therapy

Purpose: To evaluate the impact of preoperative use of intravenous contrast media (ICM) on the excellent response (ER) rates in a cohort of intermediate-risk differentiated thyroid cancer (DTC) patients who received total thyroidectomy (TT) and low-dose radioactive iodine (RAI) therapy.

Methods: A total of 683 consecutive patients were retrospectively reviewed in a single center between August 2016 and August 2018. Patients were divided into ICM group (n = 532) and non-ICM group (n = 151). Intravenous contrast media patients were 1:1 propensity matched to non-ICM patients based on T stage, N stage, and urinary iodine. Risk-adjusted logistic regression models were constructed to assess the association between the use of ICM and ER rates.

Results: Intravenous contrast media patients had significantly higher T stage (P < 0.001), N stage (P < 0.001), urinary iodine (P < 0.001), and ps-Tg (P = 0.042) than non-ICM patients. Preoperative use of ICM was found to be significantly associated with decreased ER rates in both the primary cohort [odds ratio (OR) = 0.47, 95% confidence interval (CI) = 0.32–0.71; P < 0.001] and the matched cohort (OR = 0.48, 95% CI = 0.25–0.94; P = 0.031). Subgroup analysis on RAI delay time in the primary cohort revealed that ER rates in ICM patients were significantly lower than that of non-ICM patients for 1–2 months (P = 0.0245) and >2–3 months (P = 0.0221) subgroups, but not for >3–4 months, >4–5 months, and >5–6 months subgroups (all P > 0.05). A delay time of >3–4 months exhibited the highest ER rate (63.08%) within the ICM group.

Conclusions: Preoperative use of ICM is associated with decreased ER rates in intermediate-risk DTC patients who subsequently receive TT and low-dose RAI therapy. For such patients, if ICM has already been received, an RAI delay time of >3–4 months would seem to be more appropriate to achieve better ER rates.

Impact of delayed radioiodine therapy in intermediate-/high-risk papillary thyroid carcinoma

OBJECTIVE

It remains unclear whether the time interval between total thyroidectomy and radioactive iodine therapy (RAIT) affects clinical outcomes in papillary thyroid carcinoma (PTC). Therefore, we evaluated the impact of timing of the first post-thyroidectomy RAIT in intermediate-to-high-risk PTC.

DESIGN AND PATIENTS

This retrospective propensity score-matched cohort study included 720 PTC patients who received RAIT for <90 or 90-180 days (early and delayed groups, n = 360 each) after thyroidectomy. Responses to therapy, disease-free survival (DFS) and overall survival (OS) were compared between the two groups.

RESULTS

After matching, the baseline characteristics of the 360 patients in each group were similarly adjusted. Within the first 2 years after initial therapy, the number of patients classified into excellent, indeterminate, biochemical incomplete and structural incomplete response categories were 221 (61%), 74 (21%), 39 (11%) and 26 (7%) in the early group, and 204 (57%), 73 (20%), 59 (16%) and 24 (7%) in the delayed group, respectively. There was no significant difference in response to therapy between the two groups (P = 0.183). During the median follow-up of 8.6 years, there was no significant difference in DFS (P = 0.060) and OS (P = 0.400) curves between the two groups. Delayed RAIT was not significantly associated with worse DFS (HR = 1.3, 95% CI 0.9-1.8, P = 0.061) or OS (HR = 1.5, 95% CI 0.6-3.4, P = 0.388).

CONCLUSIONS

Delaying the first RAIT until 180 days after total thyroidectomy had no impact on restaging, recurrence and mortality in intermediate-to-high-risk PTC.

Negative remnant 99mTc-pertechnetate uptake predicts excellent response to radioactive iodine therapy in low- to intermediate-risk differentiated thyroid cancer patients who have undergone total thyroidectomy

OBJECTIVE

Negative ^99mTc-pertechnetate uptake of the thyroid bed indicates the absence or a small volume of remnant thyroid tissue (RTT) after total thyroidectomy (TT). The aim of this study is to evaluate the predictive value of negative ^99mTc-pertechnetate scintigraphy for excellent response (ER) to radioactive iodine therapy (RIT) in low- to intermediate-risk differentiated thyroid cancer (DTC) patients.

PATIENTS

One-hundred and eighty-nine low- to intermediate-risk DTC patients who underwent TT, RIT with a single dose of 30 mCi and suppressive therapy with thyroid-stimulating hormone (TSH) from July 2015 to February 2016 in our hospital were retrospectively evaluated. ^99mTc-pertechnetate thyroid scintigraphy was performed just before RIT and images were reported dichotomously as negative or positive. The response of patients was assessed for 23.2 ± 3.8 months after RIT and dichotomized as excellent response (ER) or non-excellent response (NER). ^99mTc-pertechnetate uptake, age at diagnosis, gender, multifocality, T stage, N stage, preablative stimulated thyroglobulin (ps-Tg), and TSH were explored as potential predictors for ER.

RESULTS

80.68% (71/88) of patients with negative ^99mTc-pertechnetate uptake achieved ER. When patients were evaluated according to different ps-Tg levels, we found that 94.83% (55/58) of patients with ps-Tg < 1 ng/ml and negative ^99mTc-pertechnetate uptake achieved ER. Multivariate Cox regression analysis revealed that ps-Tg (P = 0.0001) and ^99mTc-pertechnetate uptake (P = 0.0473) were independent predictors for ER.

CONCLUSIONS

In addition to ps-Tg, negative ^99mTc-pertechnetate uptake is also a significant independent predictor for an excellent response in low- to intermediate-risk patients. It may be possible to omit RIT in patients with ps-Tg < 1 ng/ml and concurrent negative ^99mTc-pertechnetate uptake.