Practice trends in patients with persistent detectable thyroglobulin and negative diagnostic radioiodine whole body scans: a survey of American Thyroid Association members

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.

FDG PET/CT in differentiated thyroid cancer patients with low thyroglobulin levels

OBJECTIVE

To evaluate the usefulness of [18F]fluorodeoxyglucose (FDG) positron emissive tomography (PET)/CT in patients with low detectable thyroglobulin levels suspicious for persistent or recurrent differentiated thyroid cancer (DTC).

METHODS

A retrospective case series study evaluating FDG PET/CT in patients with detectable thyroglobulin (Tg) levels (≥0.20 and <10.00 ng/mL) after initial treatment with total thyroidectomy and I-131 thyroid remnant ablation for pT1-3aN0-1bM0 DTC. Sensitivity, specificity, positive (PPV) and negative predictive value (NPV) of FDG PET/CT were calculated.

RESULTS

Twenty-seven patients underwent FDG PET/CT. Median Tg level at FDG PET/CT was 2.00 ng/mL (range 0.30-9.00). FDG PET/CT was positive in 14 patients (51.9%): lesions suspicious for lymph node metastases were depicted in 12 patients, and lung metastases in 2. DTC was confirmed in 13/14 FDG PET/CT-positive patients. In 9/13 patients with a negative FDG PET/CT, DTC was confirmed ≤3 months after FDG PET/CT. The sensitivity, PPV, specificity and NPV were 59.1, 92.9, 80.0 and 30.8%, respectively.

CONCLUSIONS

This case series shows that FDG PET/CT might be useful to detect persistent or recurrent DTC in patients with low detectable Tg. However, when FDG PET/CT is negative, this does not rule out DTC and further investigations are necessary.

Silicon-photomultiplier-based PET/CT reduces the minimum detectable activity of iodine-124

The radioiodine isotope pair 124I/131I is used in a theranostic approach for patient-specific treatment of differentiated thyroid cancer. Lesion detectability is notably higher for 124I PET (positron emission tomography) than for 131I gamma camera imaging but can be limited for small and low uptake lesions. The recently introduced silicon-photomultiplier-based (SiPM-based) PET/CT (computed tomography) systems outperform previous-generation systems in detector sensitivity, coincidence time resolution, and spatial resolution. Hence, SiPM-based PET/CT shows an improved detectability, particularly for small lesions. In this study, we compare the size-dependant minimum detectable 124I activity (MDA) between the SiPM-based Biograph Vision and the previous-generation Biograph mCT PET/CT systems and we attempt to predict the response to 131I radioiodine therapy of lesions additionally identified on the SiPM-based system. A tumour phantom mimicking challenging conditions (derived from published patient data) was used; i.e., 6 small spheres (diameter of 3.7-9.7 mm), 9 low activity concentrations (0.25-25 kBq/mL), and a very low signal-to-background ratio (20:1). List-mode emission data (single-bed position) were divided into frames of 4, 8, 16, and 30 min. Images were reconstructed with ordinary Poisson ordered-subsets expectation maximization (OSEM), additional time-of-flight (OSEM-TOF) or TOF and point spread function modelling (OSEM-TOF+PSF). The signal-to-noise ratio and the MDA were determined. Absorbed dose estimations were performed to assess possible treatment response to high-activity 131I radioiodine therapy. The signal-to-noise ratio and the MDA were improved from the mCT to the Vision, from OSEM to OSEM-TOF and from OSEM-TOF to OSEM-TOF+PSF reconstructed images, and from shorter to longer emission times. The overall mean MDA ratio of the Vision to the mCT was 0.52 ± 0.18. The absorbed dose estimations indicate that lesions ≥ 6.5 mm with expected response to radioiodine therapy would be detectable on both systems at 4-min emission time. Additional smaller lesions of therapeutic relevance could be detected when using a SiPM-based PET system at clinically reasonable emission times. This study demonstrates that additional lesions with predicted response to 131I radioiodine therapy can be detected. Further clinical evaluation is warranted to evaluate if negative 124I PET scans on a SiPM-based system can be sufficient to preclude patients from blind radioiodine therapy.

High thyroglobulin and negative whole-body scan: no long-term benefit of empiric radioiodine therapy

PURPOSE

Around 10-27% of patients will present elevated thyroglobulin (Tg) levels and negative diagnostic whole-body scan (dxWBS) during differentiated thyroid cancer (DTC) follow-up. Empiric radioactive iodine (RAI) therapy in this context is controversial due to the lack of good quality studies in the context. The main purpose of this study is to compare long-term response to therapy status and overall survival between empiric RAI treated and untreated DTC patients.

METHODS

A retrospective study comparing differentiated thyroid cancer patients with negative diagnostic whole-body scan and elevated thyroglobulin levels submitted or not to empiric radioactive iodine therapy in a thyroid cancer referral center. The main outcome measures were ATA Response to Therapy Stratification at 6-12 months after RAI ablative dose, at 6-18 months after negative dxWBS and last follow-up visits.

RESULTS

Overall, 120 DTC patients with stimulated Tg >10 ng/ml and negative dxWBS were included in this study. Overall, 53 patients were submitted to empiric RAI and 67 were in the control group. No difference was observed in ATA Response to Therapy Stratification after RAI ablation or at the end of follow-up between groups. Also, no difference was found in terms of Tg changes response. After more than 10 years of follow-up, 17 patients died (13 from treated and 4 from untreated group).

CONCLUSIONS

Empiric RAI treatment was not associated with better long-term ATA response to therapy status or overall survival.

Correlation between F18-FDG PET/CT Imaging and BRAF V600E Genetic Mutation for the Early Assessment of Treatment Response in Papillary Thyroid Cancers

In thyroid neoplastic pathology, the BRAF V600E mutation is shown to be involved in the oncogenesis of papillary thyroid cancer and its subtypes. The purpose of this study is to evaluate the correlation between the mutation of the BRAF V600E oncogene and the pathological standardized uptake values (SUV) at the F18-fluorodeoxyglucose (F18-FDG) positron emission tomography/computed tomography (PET/CT) evaluation, for a group of 20 patients with radically treated (total thyroidectomy and radioiodine therapy) papillary thyroid cancer, with subclinical persistent disease, at 6 months after the initial treatment. We analyzed the correlations between the values of SUV and the presence of the BRAF mutation as well with other prognostic factors such as stage, age, specific tumor markers (thyroglobulin and anti-thyroglobulin), extrathyroid extension, the presence of metastatic lymph nodes or distant metastasis. The value of SUV in the case of BRAF+ (positive) patients was higher than in the negative ones, but without statistical significance, thus, the values of the SUV cannot be a predictable factor for the presence of the genetic mutation. There was a statistically significant correlation in BRAF+ subgroup between the SUV values and the positive resection limit following surgery, showing a higher SUV value in the PET/CT evaluation. No correlation was observed between the aforementioned prognostic factors involved in papillary thyroid cancer and the BRAF V600E mutation.

Revisiting 99mTc-MIBI Radioguided Surgery in Management of TENIS Syndrome

Management of patients with thyroglobulin elevated and negative iodine scan is still a challenge with limited options left as the disease stops concentrating iodine. The minimally invasive surgery is the best option for residual/recurrent locoregional disease in postsurgical setup requiring accurate presurgical localization. Intraoperative gamma probe using low-dose tracer has shown its utility in radioguided surgery. The authors present a 46-year-old man with thyroglobulin elevated and negative iodine scan showing FDG-avid left supraclavicular lymph node on whole-body F-FDG PET/CT with physiological uptake on whole-body radioactive iodine scan, where Tc-MIBI radioguided probe helped in carrying out minimally invasive surgery with excision of malignant node.

Long-term clinical outcomes of papillary thyroid carcinoma patients with biochemical incomplete response

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.

Second Radioiodine Treatment: Limited Benefit for Differentiated Thyroid Cancer With Locoregional Persistent Disease

OBJECTIVES

Radioactive iodine (RAI) treatment is often indicated after total thyroidectomy in differentiated thyroid cancer (DTC). However, its role in biochemical or locoregional persistent DTC is unclear. We aimed to investigate the effect of a second RAI treatment in patients with incomplete response to initial treatment and no evidence of distant metastases.

METHODS

Patients who underwent at least two RAI treatments over a 20-year period at a tertiary hospital were identified. Thyroglobulin levels and neck imaging were compared before and 1 to 2 years after RAI retreatment and evaluated at the last visit.

RESULTS

The cohort included 164 patients (103 female; mean age, 46.6 ± 17 years). Of 114 patients retreated without prior reoperation, 53 had structural disease. At 1 to 2 years after RAI retreatment, 10 of the 41 patients with sufficient data had structural progression, 5 resolution/shrinkage, and 26 stable disease. Stimulated thyroglobulin (stTg) measured 93.7.1 ± 108 ng/mL before and 102.2 ± 124 ng/mL after retreatment (P = NS). The other 61 patients had biochemical-only persistence. Their stTg levels decreased from 41.9 ± 56 to 24.6 ± 54 ng/mL (P = 0.003). The 50 patients who underwent neck reoperation before RAI retreatment showed no substantial change in stTg; 21 (42%) still had imaging findings 1 to 2 years later. At final follow-up, despite additional treatment in 63/164 patients (38.4%), only 56/164 (34.1%) had no evidence of disease.

CONCLUSIONS

This comprehensive study showed limited benefit of second RAI treatment in DTC patients with biochemical or locoregional structural persistent disease. Prospective studies are needed to distinguish patients for whom repeated RAI may be indicated to avoid unnecessary exposure.

Persistent Elevation of Thyroglobulin in Patient Treated for Differentiated Thyroid Cancer: A Ten-Year Review

Differentiated Thyroid Cancer (DTC) is increasing in prevalence due to better diagnostic tools and excellent long-term survival. This study is to understand the outcome of twenty-six patients with DTC over a period of 10 years after the initial treatment with surgery and radioiodine therapy. Our study analysis showed no deaths, and indicated that older men were more likely to have persistent disease. Further studies are needed to focus on cost effective long-term management of DTC.

Radioiodine Ablation following Thyroidectomy for Differentiated Thyroid Cancer: Literature Review of Utility, Dose, and Toxicity

Management recommendations for differentiated thyroid cancer are evolving. Total thyroidectomy is the backbone of curative-intent therapy, with radioiodine ablation (RAI) of the thyroid remnant routinely performed, in order to facilitate serologic surveillance and reduce recurrence risk. Several single-institution series have identified patient subsets for whom recurrence risk is sufficiently low that RAI may not be indicated. Further, the appropriate dose of RAI specific to variable clinicopathologic presentations remains poorly defined. While recent randomized trials demonstrated equivalent thyroid remnant ablation rates between low- and high-dose RAI, long-term oncologic endpoints remain unreported. While RAI may be employed to facilitate surveillance following total thyroidectomy, cancer recurrence risk reduction is not demonstrated in favorable-risk patients with tumor size ≤1 cm without high-risk pathologic features. When RAI is indicated, in patients without macroscopic residual disease or metastasis, the evidence suggests that the rate of successful remnant ablation following total thyroidectomy is equivalent between doses of 30-50 mCi and doses ≥100 mCi, with fewer acute side effects; however, in the setting of subtotal thyroidectomy or when preablation diagnostic scan uptake is >2%, higher doses are associated with improved ablation rates. Historical series demonstrate conflicting findings of long-term cancer control rates between dose levels; long-term results from modern series have yet to be reported. For high-risk patients, including those with positive surgical margins, gross extrathyroidal extension, lymph node involvement, subtotal thyroidectomy, or >5% uptake, higher-dose RAI therapy appears to provide superior rates of ablation and cancer control.

Use of imaging tests after primary treatment of thyroid cancer in the United States: population based retrospective cohort study evaluating death and recurrence

OBJECTIVE

 To determine whether the use of imaging tests after primary treatment of differentiated thyroid cancer is associated with more treatment for recurrence and fewer deaths from the disease.

DESIGN

 Population based retrospective cohort study.

SETTING

 Surveillance Epidemiology and End Results-Medicare database in the United States.

PARTICIPANTS

 28 220 patients diagnosed with differentiated thyroid cancer between 1998 and 2011. The study cohort was followed up to 2013, with a median follow-up of 69 months.

MAIN OUTCOME MEASURES

 Treatment for recurrence of differentiated thyroid cancer (additional neck surgery, additional radioactive iodine treatment, or radiotherapy), and deaths due to differentiated thyroid cancer. We conducted propensity score analyses to assess the relation between imaging (neck ultrasound, radioiodine scanning, or positron emission tomography (PET) scanning) and treatment for recurrence (logistic model) and death (Cox proportional hazards model).

RESULTS

 From 1998 until 2011, we saw an increase in incident cancer (rate ratio 1.05, 95% confidence interval 1.05 to 1.06), imaging (1.13, 1.12 to 1.13), and treatment for recurrence (1.01, 1.01 to 1.02); the change in death rate was not significant. In multivariable analysis, use of neck ultrasounds increased the likelihood of additional surgery (odds ratio 2.30, 95% confidence interval 2.05 to 2.58) and additional radioactive iodine treatment (1.45, 1.26 to 1.69). Radioiodine scans were associated with additional surgery (odds ratio 3.39, 95% confidence interval 3.06 to 3.76), additional radioactive iodine treatment (17.83, 14.49 to 22.16), and radiotherapy (1.89, 1.71 to 2.10). Use of PET scans was associated with additional surgery (odds ratio 2.31, 95% confidence interval 2.09 to 2.55), additional radioactive iodine treatment (2.13, 1.89 to 2.40), and radiotherapy (4.98, 4.52 to 5.49). Use of neck ultrasounds or PET scans did not significantly affect disease specific survival (hazard ratio 1.14, 95% confidence interval 0.98 to 1.27, and 0.91, 0.77 to 1.07, respectively). However, radioiodine scans were associated with an improved disease specific survival (hazard ratio 0.70, 95% confidence interval 0.60 to 0.82).

CONCLUSIONS

 The marked rise in use of imaging tests after primary treatment of differentiated thyroid cancer has been associated with an increased treatment for recurrence. However, with the exception of radioiodine scans in presumed iodine avid disease, this association has shown no clear improvement in disease specific survival. These findings emphasize the importance of curbing unnecessary imaging and tailoring imaging after primary treatment to patient risk.

Evaluating Positron Emission Tomography Use in Differentiated Thyroid Cancer

BACKGROUND

Using the Surveillance, Epidemiology, and End Results-Medicare database, a substantial increase was found in the use of positron emission tomography (PET) scans after 2004 in differentiated thyroid cancer (DTC) patients. The reason for the increased utilization of the PET scan was not clear based on available the data. Therefore, the indications for and outcomes of PET scans performed at an academic institution were evaluated.

METHODS

A retrospective cohort study was performed of DTC patients who underwent surgery at the University of Michigan Health System from 2006 to 2011. After identifying patients who underwent a PET scan, indications, rate of positive PET scans, and impact on management were evaluated. For positive scans, the location of disease was characterized, and presence of disease on other imaging was determined.

RESULTS

Of the 585 patients in the cohort, 111 (19%) patients had 200 PET scans performed for evaluation of DTC. Indications for PET scan included: elevated thyroglobulin and negative radioiodine scan in 52 scans (26.0%), thyroglobulin antibodies in 13 scans (6.5%), rising thyroglobulin in 18 scans (9.0%), evaluation of abnormality on other imaging in 22 scans (11.0%), evaluation of extent of disease in 33 scans (16.5%), follow-up of previous scan in 57 scans (28.5%), other indications in two scans (1.0%), and unclear indications in three scans (1.5%). The PET scan was positive in 124 studies (62.0%); positivity was identified in the thyroid bed on 25 scans, cervical or mediastinal lymph nodes on 105 scans, lung on 28 scans, bone on four scans, and other areas on 14 scans. Therapy following PET scan was surgery in 66 cases (33.0%), chemotherapy or radiation in 23 cases (11.5%), observation in 110 cases (55.0%), and palliative care in one case (0.5%). Disease was identifiable on other imaging in 66% of cases. PET scan results changed management in 59 cases (29.5%).

CONCLUSIONS

In this academic medical center, the PET scan was utilized in 19% of patients. Indications for the PET scan included conventional indications, such as elevated thyroglobulin with noniodine avid disease, and more controversial uses, such as evaluation of extent of disease or abnormalities on other imaging tests. PET scan results changed management in about 30% of cases.

Does (131)I Radioactivity Interfere with Thyroglobulin Measurement in Patients Undergoing Radioactive Iodine Therapy with Recombinant Human TSH?

OBJECTIVES

Recombinant human thyroid-stimulating hormone (rhTSH) is widely used in radioactive iodine therapy (RIT) to avoid side effects caused by hypothyroidism during the therapy. Owing to RIT with rhTSH, serum thyroglobulin (Tg) is measured with high (131)I concentrations. It is of concern that the relatively high energy of (131)I could interfere with Tg measurement using the immunoradiometric assay (IRMA). We investigated the effect of (131)I administration on Tg measurement with IRMA after RIT.

METHODS

A total of 67 patients with thyroid cancer were analysed retrospectively. All patients had undergone rhTSH stimulation for RIT. The patients' sera were sampled 2 days after (131)I administration and divided into two portions: for Tg measurements on days 2 and 32 after (131)I administration. The count per minute (CPM) of whole serum (200 μl) was also measured at each time point. Student's paired t-test and Pearson's correlation analyses were performed for statistical analysis.

RESULTS

Serum Tg levels were significantly concordant between days 2 and 32, irrespective of the serum CPM. Subgroup analysis was performed by classification based on the (131)I dose. No difference was noted between the results of the two groups.

CONCLUSIONS

IRMA using (125)I did not show interference from (131)I in the serum of patients stimulated by rhTSH.