Abstract
Objective
Patients with non-medullary thyroid carcinoma (NMTC) that are refractory to radioactive iodine (RAI) have a poor prognosis. Strategies for restoring the ability to take up iodine, so-called redifferentiation, are promising but not suitable for all patients. Preclinical studies, in human cell lines just as in a murine model, have shown that the cardiac glycoside digoxin restored RAI uptake. This prospective single-center open-label study aimed to investigate whether treatment with digoxin could reinduce clinically relevant RAI uptake in patients with metastasized RAI-refractory NMTC.
Methods
Eight patients with metastasized RAI-refractory NMTC were included between November 2022 and June 2023. Before treatment, a baseline [123I]NaI scintigraphy was performed. Thereafter, patients were treated with digoxin for 3 weeks. Starting doses depended on age and weight. For safety reasons, the usual therapeutic range was aimed for. After 1 week, the digoxin plasma concentration was measured, and the digoxin dose was adjusted if necessary. After 3 weeks of digoxin treatment, a second [123I]NaI scintigraphy was performed. RAI uptake was compared between the two scintigraphies.
Results
Seven patients completed the digoxin treatment and were evaluable. None of the seven patients showed clinically relevant RAI uptake after digoxin treatment. No digoxin-related serious adverse events occurred during this trial.
Conclusion
Contrary to results from preclinical trials, in this trial, 3 weeks of digoxin treatment did not reinduce RAI uptake in patients with NMTC. This highlights essential challenges regarding the approach toward optimization of studies aimed to restore the RAI uptake and its therapeutic efficacy through drug repurposing.
Introduction
The large majority of patients with non-medullary thyroid carcinoma (NMTC) have an excellent prognosis and achieve remission after conventional treatment by surgery, radioactive iodine (RAI) treatment, and levothyroxine replacement (1). The prognosis worsens significantly if patients develop recurrent and metastatic disease, particularly when the tumors are refractory to RAI (2, 3, 4). In the last decades, there have been several attempts to develop strategies that re-enable treatment with RAI for tumors previously deemed RAI refractory, potentially providing patients with new treatment options (5).
RAI resistance can be the consequence of the so-called NMTC ‘dedifferentiation’, which is a process in which the accumulation of genetic mutations (such as BRAF, TP53, PTEN, and TERT promoter mutations) in MAPK- and PI3K-pathways leads to loss of thyroid-specific cell properties. A hallmark of NMTC dedifferentiation is the loss of expression of thyroid-specific genes such as the Na/I symporter (NIS) or thyroid peroxidase (TPO) or the loss of function of their products, resulting in reduced RAI uptake and resistance to RAI (6, 7). Other possible explanations include the rapid release of iodine from tumor cells and resistance to RAI-induced apoptosis (8). Strategies for restoring thyroid-specific gene expression by so-called ‘redifferentiation’, and thus NIS and TPO expression and function, followed by the administration of RAI, are promising treatment modalities. Several case reports, case series, and phase II trials have shown the capacity of MEK, BRAF, RET, and TRK inhibitors to reinduce RAI uptake in NMTC patients with specific genetic profiles (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22). Although these results are promising, other clinical trials have shown no improvement in RAI uptake after ‘redifferentiation’ treatment (23). In addition, it is important to note that the mentioned kinase inhibitors can be accompanied by non-negligible side effects. Moreover, not all RAI-refractory NMTC patients harbor established mutations that make them eligible for treatment with these inhibitors.
Preclinical studies have demonstrated that the cardiac glycoside digoxin restores NIS expression and increases RAI uptake capacity in NMTC cells, both in human cell lines and in an in vivo murine model (24, 25). The results were supported by a retrospective study showing that NMTC patients treated with digoxin for cardiac indications showed better clinical responses to RAI treatment compared to matched NMTC patients who were not treated with digoxin (25). Another in vitro study showed that digoxin could also restore NIS expression in anaplastic thyroid carcinoma cell lines (26). The mechanism responsible for digoxin-induced redifferentiation might be related to the upregulation of NIS expression mediated by intracellular Ca+2 and FOS activation (27). In this prospective single-center open-label proof-of-principle study, we investigated whether treatment with digoxin could reinduce clinically relevant RAI uptake in patients with metastasized and RAI-refractory NMTC.
Subjects and methods
Patient selection
Patients were recruited at the Radboud University Medical Center, Nijmegen, the Netherlands. To be eligible for this study, patients had to be aged ≥18 years, have been diagnosed with NMTC, have undergone a total thyroidectomy, and have received at least one treatment with RAI. In addition, patients had to have radiologically proven metastases or local recurrent disease, and there had to be at least one target lesion with a size of at least 10 mm (15 mm in the case of lymph node metastases) that did not accumulate RAI at a previous post-therapeutic or diagnostic RAI-scintigraphy. Major exclusion criteria were prior RAI treatment <6 months before initiation of digoxin treatment, having received intravenous iodine <3 months before digoxin treatment, having received systemic anti-cancer therapy or radiotherapy <4 weeks before digoxin treatment, other active malignancies, a creatinine clearance <50 mL/min, cardiac arrhythmias, severe electrolyte disorders, and concomitant use of drugs interfering with digoxin metabolism. The full list of inclusion and exclusion criteria can be found in Supplementary Table 1 (see the section on supplementary materials given at the end of this article).
This study was approved by the medical research ethics committee NedMec under the Clinical Trials Regulation (no. 2022-500477-14-00) and was registered at ClinicalTrials.gov (NCT05507775). All participants provided written informed consent, and all study procedures were conducted according to the principles expressed in the Declaration of Helsinki.
Procedures
Figure 1 shows a flowchart describing the study procedures. In the screening phase, blood was drawn to exclude renal impairment and severe electrolyte disorders. In addition, an electrocardiogram was made to exclude cardiac arrhythmias. When deemed eligible, patients underwent [123I]NaI scintigraphy (148 MBq) on day 0 preceded by recombinant human thyrotropin (rhTSH, Thyrogen®) injections of 0.9 mg on days 1 and 2. On day 1, patients started oral digoxin treatment. All patients were treated with Lanoxin®. Patients aged >70 years or with body weight <55 kg started with a dose of 0.125 mg once daily. Other patients started with a dose of 0.250 mg once daily. On day 7, the blood plasma concentration of digoxin was measured. When the concentration exceeded 2.0 ng/L, the dose was reduced by 50%. When the concentration was below the therapeutic range, the dose was increased to 0.250 mg or 0.375 mg once daily for patients using 0.125 mg or 0.250 mg once daily, respectively. The new dose was then continued until the second [123I]NaI scintigraphy on day 21 and again preceded by rhTSH injections on days 19 and 20. Thyroid hormone replacement was continued during the whole study. [123I]NaI scintigraphies were assessed by a nuclear medicine physician with expertise in thyroid carcinoma (JN).
Overview of the study procedures.
Citation: European Thyroid Journal 13, 4; 10.1530/ETJ-24-0153
In the case of clinically relevant [123I]NaI uptake on day 21, defined as higher uptake in metastases than uptake in the liver, a [131I]NaI treatment would be offered to the patient and would take place ±1 week after the second [123I]NaI scintigraphy, preceded by two injections of rhTSH. Digoxin treatment would then be continued until the administration of [131I]NaI.
In the case of no clinically relevant [123I]NaI uptake on day 21, no [131I]NaI treatment could be offered, and digoxin treatment was discontinued immediately. Mutational analysis was performed on formalin-fixed paraffin-embedded tissue from the primary tumor using the predictive analysis for therapy panel, and fusion gene analysis was performed using the custom-designed Archer FusionPlex® Radboudv1 panel (28). Toxicity and safety were assessed on day 7 and day 21 according to the Common Terminology Criteria for Adverse Events version 5.0.
In vitro experiment
NMTC cell lines FTC133 (follicular, PTEN, and TP53 mutations) and TPC1 (papillary, RET/PTC rearrangement) were cultured in Roswell Park Memorial Institute 1640 medium + GlutaMAX (Thermo Fisher) supplemented with penicillin/streptomycin (10 µg/mL) and 10% fetal calf serum. Cells were incubated with digoxin (Sigma-Aldrich, dissolved in DMSO) or DMSO as a vehicle control. After 72 h of incubation, cells were detached and stained with Fixed Viability Stain 620 (Live/Dead stain, BD Biosciences) and SLC5A5 Alexa Fluor 647 (R&D Bio-techne) antibodies. After 15 min of staining, the NIS expression was measured in stained and unstained samples on a CytoFlex flow cytometer (Beckman Coulter).
Analysis
The primary outcome was the proportion of evaluable patients in whom there was reinduction of clinically relevant RAI uptake after 3 weeks of digoxin treatment. The study was predefined to be successful if more than three patients showed reinduction of RAI uptake. With a planned sample size of ten subjects, a type I error rate of 5%, and a population proportion of <10%, this gave the study a power of 80%. A secondary outcome was the toxicity and safety of digoxin treatment. Baseline characteristics are displayed as median with range. In the in vitro experiment, median fluorescence index was analyzed using FlowJo Software (v10.8, BD Biosciences) and compared between conditions.
Results
Between November 2022 and June 2023, eight RAI-refractory NMTC patients were enrolled, of which seven were evaluable for reinduction of RAI uptake after 3 weeks of digoxin treatment. Figure 2 shows the process of screening and enrollment. The clinical characteristics of the enrolled patients are included in Table 1.
Flowchart describing the screening for eligibility and inclusion of patients.
Citation: European Thyroid Journal 13, 4; 10.1530/ETJ-24-0153
Clinical characteristics of evaluable patients at baseline. Data are presented as n or as median (IQR).
| Characteristics | Values |
|---|---|
| Patients evaluated | 7 |
| Age, years | 60 (54–72) |
| Sex - male/female | 3/4 |
| WHO performance status at diagnosis | |
| 0 | 2 |
| 1 | 5 |
| Years since diagnosis | 8 (2–10) |
| Locations of metastases at inclusion | |
| Lungs | 7 |
| Liver | 2 |
| Lymph nodes | 5 |
| Bones | 1 |
| Tumor histology | |
| Papillary thyroid carcinoma | 5 |
| Follicular variant | 2 |
| Tall cell | 1 |
| Unavailable | 2 |
| Oncocytic thyroid carcinoma | 2 |
| Tumor genotype, | |
| BRAFV600E | 2 |
| NRAS | 1 |
| HRAS | 1 |
| PTEN | 1 |
| TP53 | 1 |
| Serum FT4 concentration, pmol/L | 25.0 (21.7–26.4 ) |
| Serum TSH concentration, mU/L | 0.04 (0.02–0.82) |
| Daily levothyroxine dose, μg | 175.0 (112.5–187.5) |
| Prior RAI treatments | 3 (1–4) |
| Cummulative dose of prior RAI treatments | |
| mCi | 400 (200–600) |
| GBq | 14.8 (7.4–22.2) |
| Other previous thyroid cancer | |
| External-beam radiation therapy | 2 |
| Targeted therapy | 0 |
After 7 days, the median digoxin concentration was 0.6 µg/L (range: 0.5–1.9 µg/L), and the dose was increased in six out of seven patients. The median digoxin concentration at day 21 was 0.8 µg/L (range: 0.6–1.0 µg/L). At day 21, two patients were treated with 0.250 mg per day, and five patients were treated with 0.375 mg per day.
None of the evaluable patients showed reinduction of RAI uptake, whether clinically relevant or not, after 3 weeks of digoxin treatment. Figure 3 shows [123I]NaI scintigraphies before and after digoxin treatment, showing no induction of RAI uptake. Because it was not possible to reach the four patients with a positive result that was predefined to assess the treatment as successful, enrollment was stopped.
[123I]NaI scintigraphies before (A) and after (B) 3 weeks of digoxin treatment, showing no induction of RAI uptake in the pulmonal metastases in this patient (C).
Citation: European Thyroid Journal 13, 4; 10.1530/ETJ-24-0153
During the study, one non-digoxin-related serious adverse event occurred in a patient who was admitted for pneumonia. This patient received an iodinated contrast agent for a diagnostic scan to rule out a pulmonary embolism and was subsequently excluded from the study. Increased fatigue was the only adverse event occurring in more than one patient during the trial, presenting in four out of seven evaluable patients. Digoxin treatment was temporarily withdrawn for 2 days in one patient because of grade 2 nausea. In addition, one patient developed thyroglobulin antibodies during digoxin treatment.
In vitro experiment
The negative result of the current study is in contrast to the results of previous preclinical studies, where exposure to digoxin did increase the NIS expression and RAI uptake in cell lines and mice (24, 25). One possible explanation for this discrepancy is that the serum digoxin concentrations in the current study’s participants were lower than the concentrations used in the in vitro and murine experiments. Therefore, an in vitro experiment using cell lines was performed using digoxin concentrations comparable to participants’ serum concentrations. As shown in Supplementary Figure 1, 72 h of incubation with 50 nM or 0.025 nM indeed does not significantly increase the NIS expression in TPC1 and FTC133 cell lines.
Discussion
The present study is the first prospective trial in humans to assess the redifferentiation potential of digoxin in patients with RAI-refractory NMTC. In this study, both male and female patients with different NMTC subtypes and driver mutations and different metastatic locations were included. Although digoxin treatment was safe and resulted in only minimal toxicity, in none of the seven evaluable patients there was clinically relevant reinduction of RAI uptake after 3 weeks of digoxin treatment warranting RAI treatment. This indicates that treatment with digoxin, at least according to the protocol used in this study, does not lead to clinically relevant redifferentiation. Nonetheless, the knowledge gathered in our study is valuable and can help guide the design of future studies in which drugs can be repositioned for redifferentiation and/or uptake enhancement in NMTC.
Previous preclinical studies showed promising results regarding digoxin and other digitalis-like compounds as a possible treatment modality for patients with RAI-refractory NMTC. In vitro studies with different NMTC cell lines showed that incubation with digoxin increased thyroid-specific gene expression, hNIS expression, and RAI (125I) uptake (24). Furthermore, another study showed that a 3-week digoxin treatment of tumor-bearing BRAFV600E mutant mice resulted in elevated expression of several thyroid-specific genes and increased RAI [124I] uptake (25). Moreover, digoxin treatment inhibited tumor growth. The latter study also retrospectively compared NMTC tissue of patients who were treated with digoxin for cardiac indications with tissue of NMTC patients that were not treated with digoxin and that were matched for age, sex, histological NMTC subtype, TNM staging at diagnosis, and tumor mutation status (25). RNA-sequencing-based expression analysis showed higher expression of thyroid-specific genes in patients who were treated with digoxin. Moreover, the digoxin-treated patients showed more favorable clinical outcomes, defined as disease status after RAI ablation and NMTC-related mortality.
There are several possible explanations for the lack of redifferentiation observed in the present human trial. First, this being the first intervention trial on repurposing digoxin for the redifferentiation of NMTC, it was not possible to establish the effective dose of the medication for this purpose. For safety considerations, we kept the dose of digoxin within the known therapeutic range. This dose may have been insufficient to achieve the required effect at the tumor level. The digoxin doses that were previously used in the in vitro experiments and in the mouse model were higher than the dose used in the present study (24, 25). To assess whether this difference could partially explain why digoxin treatment did not lead to increased RAI uptake in the current study, an in vitro experiment was performed using digoxin concentrations comparable to serum concentrations in the current study. Indeed, these concentrations did not lead to increased NIS expression. Regarding the mouse model, it has been shown that murine cells are less sensitive to digoxin-mediated effects compared to human cells because the α1 subunit of murine Na+/K+ ATPase binds to digoxin less strongly than its human counterpart (29, 30). In addition, the route of administration in the mouse study (intraperitoneal) differed from the oral administration in our study. In order to make future redifferentiation studies in mice and other rodents more translatable to human studies, gavage drug administration, instead of intraperitoneal administration, in rodents could be considered. Secondly, in the mouse study, all tumors were BRAF mutated, while in the present study, NMTC patients were included that had different driver mutations. The driver mutation analysis was done on the primary tumor, as there was no target lesion deemed accessible for a new biopsy in the included patients. Nonetheless, the two patients in the present study with BRAFV600E mutations in the primary tumor did not show increased uptake of RAI after digoxin treatment. Thirdly, the optimal duration of the treatment with digoxin to elicit the upregulation of NIS is not known. Notably, the patients included in the retrospective NMTC tissue comparison all used digoxin before their NMTC diagnosis and were treated for variable periods (the median duration of digoxin treatment before NMTC diagnosis was 14 weeks with a range of 4 weeks to 10.5 years), while the patients in the present study started digoxin treatment years after diagnosis and were treated for 3 weeks (25). This 3-week treatment was based on the observations in the mouse model in which restoration of RAI uptake could already be seen after only 5 days of digoxin treatment, and this remained stable after 3 weeks of digoxin treatment. This suggests that 3 weeks of digoxin treatment should be appropriate to show stable effects of redifferentiation. In redifferentiation studies using other agents, a treatment duration of approximately 3 weeks has been sufficient to elicit enhanced RAI uptake (9, 10, 11, 12, 14, 17, 18, 31). Finally, while the patients in our study were chronically treated with high doses of levothyroxine to suppress their TSH, the mice in the mouse study were not (25). Additionally, media used in the NMTC cell line studies were only supplemented with 10% fetal calf serum but not with high doses of levothyroxine (24). Studies have shown that TSH itself can enhance the (mRNA) expression of several thyroid-specific genes in cell lines (32, 33). Despite the fact that the patients in our study received rhTSH before the diagnostic scans, previous TSH suppression could thus hypothetically negatively impact NMTC redifferentiation. Future preclinical studies could consider suppressing TSH in rodents in order to increase the validity and reproducibility in human studies.
The present study has limitations, some of which might have mitigated the effect on RAI uptake in our patients. We cannot assess the effectiveness of the digoxin treatment on the thyroid-specific gene expression (and thus differentiation status) in the target lesions. For this, tissue biopsies before and after digoxin treatment would have been required, which was not possible for the included patients. Likewise, no dosimetric imaging was used to quantify RAI uptake. Although these data could have provided more quantitative information on the absorbed dose delivered, from a clinical point of view they would have been of limited additional value compared to the diagnostic scans in revealing robust clinically relevant RAI uptake and the subsequent option to undergo successful [131I]NaI treatment. Therefore, we consider that a higher thyroid differentiation score or statistically significantly higher RAI uptake would not have made digoxin a feasible treatment modality in the absence of clinically relevant RAI uptake. In addition, it should be mentioned that several studies have shown that [123I]NaI scintigraphy has a lower sensitivity for NMTC metastases than post-therapy [131I]NaI scintigraphy (34, 35, 36). Administering a therapeutic [131I]NaI activity could have been an option that could have helped compensate for the lack of pretreatment dosimetry data and provided more reliable and sensitive information on the potential uptake enhancement. However, for safety concerns, given that several of the patients included in the study have already had multiple therapies, we refrained from a treatment that was not considered beneficial. Another limitation is that we could not assess the intratumoral digoxin concentration that might help adjust the protocol in the future. Nonetheless, given that all patients achieved blood digoxin concentrations within the therapeutic range, it is highly unlikely that achieving a higher concentration is feasible in clinical practice, taking safety into account. Moreover, because of the exploratory nature of the study, it has not been powered to detect potential positive results. Nonetheless, this power calculation did not consider the heterogeneity of the cohort in terms of histological subtypes and the genetic background of the tumor, which should likely be accounted for in future studies.
Several studies (phase II studies, pilot studies, case series, and case reports), summarized in Table 2, have shown some efficacy of different kinase inhibitors (BRAF inhibitors dabrafenib and vemurafenib, MEK inhibitors trametinib and selumetinib, RET inhibitor selpercatinib, and TRK inhibitor larotrectinib) regarding the enhancement of RAI uptake in RAI-refractory NMTC patients. Although these results are promising, particularly in well-selected patients, the body of evidence is still very limited. In most studies, only patients with certain histological subtypes and genotypes were included. The treatment protocols and study procedures, including the patient selection, duration of treatment, assessment of treatment effectiveness, and outcome measures vary significantly between the studies. Moreover, even short treatment with these agents can be accompanied by non-negligible side effects. In a prospective trial that included RAI-refractory NMTC patients with different histological subtypes and genotypes, the multikinase inhibitor sorafenib did not reinduce RAI uptake in RAI-refractory NMTC patients (23). So, while there are some valid options for redifferentiation therapy in specific groups of RAI-refractory NMTC patients, for most patients, redifferentiation options are lacking.
Overview of human studies showing effective reinduction of radioactive iodine uptake in RAI-refractory NMTC patients.
| Study | Studied agent(s) | Study type | Treatment duration | Included NMTC subtype(s) | Included genotype(s) | Patients evaluated, n | Patients with increased RAI uptake, n |
|---|---|---|---|---|---|---|---|
| Tchekmedyian et al. (19) | Vemurafenib + anti-ErbB3 antibody (CDX-3379) | Pilot trial | 5 weeks | PTC, PDTC | BRAFV600E | 6 | 5/6 |
| Leboulleux et al. (9) | Dabrafenib + trametinib | Phase II trial | 5 weeks | PTC, PDTC | BRAFV600E | 21 | 20/21 |
| Rothenberg et al. (11) | Dabrafenib | Pilot trial | 4 weeks | PTC | BRAFV600E | 10 | 6/10 |
| Weber et al. (31) | Trametinib for BRAF-wild type patients or trametinib + dabrafenib for BRAF-mutated patients | Phase II trial | 3 weeks | PTC, FTC, PDTC | Various: BRAF, TERT promoter, PTEN, NRAS, KRAS, APC, AKT1 | 20 | 7/20 |
| Ho et al. (10) | Selumetinib | Pilot trial | 4 weeks | PTC, PDTC | Various: BRAFV600E, NRAS, RET fusion | 20 | 12/20 |
| Dunn et al. (14) | Vemurafenib | Pilot trial | 4 weeks | PTC, PDTC | BRAFV600E | 10 | 6/10 |
| Jaber et al. (13) | BRAF inhibitors or MEK inhibitors | Retrospective cohort study | Various | PTC, FTC, PDTC | BRAFV600E | 13 | 8/13 |
| Iravani et al. (15) | Trametinib, dabrafenib + trametinib or vemurafenib + cobimetinib | Retrospective cohort study | Various | PTC, FTC, PDTC | BRAFV600E, NRAS | 6 | 4/6 |
| Lee et al. (16) | Larotrectinib or Selpercatinib | Case series | 4–5 months | Pediatric PTC | NTRK rearrangement or RET fusion | 2 | 2/2 |
| Groussin et al. (20) | Larotrectinib | Case series | 20–30 days | PTC | NTRK rearrangement | 3 | 2/3 |
| Leboulleux et al. (21) | Dabrafenib + trametinib | Case report | 2 months | PDTC | BRAFK601E | 1 | 1/1 |
| Jafri et al. (22) | Dabrafenib + trametinib |
Case report | 1 month | PTC | BRAFV600E | 1 | 1/1 |
| Huillard et al. (12) | Vemurafenib | Case report | 3 months | PTC | BRAFV600E | 1 | 1/1 |
| Groussin et al. (18) | Larotrectinib | Case report | 3 weeks | PTC | NTRK fusion | 1 | 1/1 |
| Groussin et al. (17) | Selpercatinib | Case report | 3 weeks | PTC | RET fusion | 1 | 1/1 |
FTC, follicular thyroid carcinoma; PDTC, poorly differentiated thyroid carcinoma;PTC, papillary thyroid carcinoma.
For future human studies on redifferentiation strategies in patients with RAI-refractory NMTC, based on our experience with the current study, we suggest the following considerations that could improve the likelihood of obtaining clinically meaningful data. First, in our opinion, studies should primarily focus on clinically relevant RAI uptake that could justify subsequent treatment (in our study defined as higher uptake in the metastases than in the liver) and if possible on clinical outcomes rather than statistically significant enhanced RAI uptake. For this, a uniform definition and a uniform procedure to assess clinically relevant RAI uptake are needed. Furthermore, efforts are needed to establish the patients who are most likely to achieve successful redifferentiation considering both the enhancement of RAI uptake and the delivery of effective radiation. For example, oncocytic follicular thyroid carcinoma has been associated with intrinsically less RAI uptake than papillary or follicular thyroid carcinomas (37, 38). This questions whether redifferentiation therapy is less likely to result in clinically relevant RAI uptake in patients with oncocytic tumors than in patients with other NMTC subtypes. Also, patients who have shown previous uptake in certain lesions may have a better chance of a successful enhancement of RAI uptake and subsequent delivery of the required effective activity. In addition, future studies should take into account the heterogeneity of NMTC tumors. Separate metastases can display different genotypes, hypothetically resulting in different responses to redifferentiation therapy. It will be important to consider this while defining ‘successful redifferentiation’. Furthermore, some tissue types are more sensitive to radiation than others, e.g. lung lesions respond to lower radiation doses than bone metastases. Therefore, this factor could also be used to guide the selection of patients for a successful redifferentiation. Finally, future studies should focus on new methods to monitor the efficacy of redifferentiation therapies. Hypothetically, an increase in serum thyroglobulin levels could be indicative of upregulated expression of thyroid-specific genes and thus redifferentiation. However, it can also represent disease progression. Future studies should investigate the utility of thyroglobulin and other biomarkers as markers of redifferentiation.
Conclusion
In conclusion, contrary to results from preclinical trials, in this study, digoxin treatment does not reinduce RAI uptake in patients with RAI-refractory NMTC. Future studies are needed to identify effective redifferentiation strategies in RAI-refractory NMTC patients not eligible for specific kinase inhibitors. Caution should be taken to translate preclinical results to clinical applications for redifferentiation purposes.
Supplementary materials
This is linked to the online version of the paper at https://doi.org/10.1530/ETJ-24-0153.
Declaration of interest
The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the study reported.
Funding
This work was supported by the Dutch Cancer Society (Grant no. 2021-2/13771).
References
- 1↑
Pizzato M, Li M, Vignat J, Laversanne M, Singh D, La Vecchia C, & Vaccarella S. The epidemiological landscape of thyroid cancer worldwide: GLOBOCAN estimates for incidence and mortality rates in 2020. Lancet. Diabetes and Endocrinology 2022 10 264–272. (https://doi.org/10.1016/S2213-8587(2200035-3)
- 2↑
Tuttle RM, Ahuja S, Avram AM, Bernet VJ, Bourguet P, Daniels GH, Dillehay G, Draganescu C, Flux G, Führer D, et al. Controversies, consensus, and collaboration in the use of 131I therapy in differentiated thyroid cancer: a joint statement from the American Thyroid Association, the European Association of Nuclear Medicine, the Society of Nuclear Medicine and Molecular Imaging, and the European Thyroid Association. Thyroid 2019 29 461–470. (https://doi.org/10.1089/thy.2018.0597)
- 3↑
Fugazzola L, Elisei R, Fuhrer D, Jarzab B, Leboulleux S, Newbold K, & Smit J. 2019 European Thyroid association guidelines for the treatment and follow-up of advanced radioiodine-refractory thyroid cancer. European Thyroid Journal 2019 8 227–245. (https://doi.org/10.1159/000502229)
- 4↑
Durante C, Haddy N, Baudin E, Leboulleux S, Hartl D, Travagli JP, Caillou B, Ricard M, Lumbroso JD, De Vathaire F, et al. Long-term outcome of 444 patients with distant metastases from papillary and follicular thyroid carcinoma: benefits and limits of radioiodine therapy. Journal of Clinical Endocrinology and Metabolism 2006 91 2892–2899. (https://doi.org/10.1210/jc.2005-2838)
- 5↑
Van Nostrand D, Veytsman I, Kulkarni K, Heimlich L, & Burman KD. Redifferentiation of differentiated thyroid cancer: clinical insights from a narrative review of literature. Thyroid 2023 33 674–681. (https://doi.org/10.1089/thy.2022.0632)
- 6↑
Aashiq M, Silverman DA, Na’ara S, Takahashi H, & Amit M. Radioiodine-refractory thyroid cancer: molecular basis of redifferentiation therapies, management, and novel therapies. Cancers 2019 11 1382. (https://doi.org/10.3390/cancers11091382)
- 7↑
Lamartina L, Anizan N, Dupuy C, Leboulleux S, & Schlumberger M. Redifferentiation-facilitated radioiodine therapy in thyroid cancer. Endocrine-Related Cancer 2021 28 T179–T191. (https://doi.org/10.1530/ERC-21-0024)
- 8↑
Tesselaar MH, Smit JW, Nagarajah J, Netea-Maier RT, & Plantinga TS. Pathological processes and therapeutic advances in radioiodide refractory thyroid cancer. Journal of Molecular Endocrinology 2017 59 R141–R154. (https://doi.org/10.1530/JME-17-0134)
- 9↑
Leboulleux S, Do Cao C, Zerdoud S, Attard M, Bournaud C, Lacroix L, Benisvy D, Taïeb D, Bardet S, Terroir-Cassou-Mounat M, et al. A Phase II redifferentiation trial with Dabrafenib-Trametinib and 131I in metastatic radioactive iodine refractory BRAF p. V600E-mutated differentiated thyroid cancer. Clinical Cancer Research 2023 29 2401–2409. (https://doi.org/10.1158/1078-0432.CCR-23-0046)
- 10↑
Ho AL, Grewal RK, Leboeuf R, Sherman EJ, Pfister DG, Deandreis D, Pentlow KS, Zanzonico PB, Haque S, Gavane S, et al. Selumetinib-enhanced radioiodine uptake in advanced thyroid cancer. New England Journal of Medicine 2013 368 623–632. (https://doi.org/10.1056/NEJMoa1209288)
- 11↑
Rothenberg SM, McFadden DG, Palmer EL, Daniels GH, & Wirth LJ. Redifferentiation of iodine-refractory BRAF V600E-mutant metastatic papillary thyroid cancer with dabrafenib. Clinical Cancer Research 2015 21 1028–1035. (https://doi.org/10.1158/1078-0432.CCR-14-2915)
- 12↑
Huillard O, Tenenbaum F, Clerc J, Goldwasser F, & Groussin L. Restoring radioiodine uptake in BRAF V600E–mutated papillary thyroid cancer. Journal of the Endocrine Society 2017 1 285–287. (https://doi.org/10.1210/js.2016-1114)
- 13↑
Jaber T, Waguespack SG, Cabanillas ME, Elbanan M, Vu T, Dadu R, Sherman SI, Amit M, Santos EB, Zafereo M, et al. Targeted therapy in advanced thyroid cancer to resensitize tumors to radioactive iodine. Journal of Clinical Endocrinology and Metabolism 2018 103 3698–3705. (https://doi.org/10.1210/jc.2018-00612)
- 14↑
Dunn LA, Sherman EJ, Baxi SS, Tchekmedyian V, Grewal RK, Larson SM, Pentlow KS, Haque S, Tuttle RM, Sabra MM, et al. Vemurafenib redifferentiation of BRAF mutant, RAI-refractory thyroid cancers. Journal of Clinical Endocrinology and Metabolism 2019 104 1417–1428. (https://doi.org/10.1210/jc.2018-01478)
- 15↑
Iravani A, Solomon B, Pattison DA, Jackson P, Ravi Kumar A, Kong G, Hofman MS, Akhurst T, & Hicks RJ. Mitogen-activated protein kinase pathway inhibition for redifferentiation of radioiodine refractory differentiated thyroid cancer: an evolving protocol. Thyroid 2019 29 1634–1645. (https://doi.org/10.1089/thy.2019.0143)
- 16↑
Lee YA, Lee H, Im S-W, Song YS, Oh D-Y, Kang HJ, Won J-K, Jung KC, Kwon D, Chung E-J, et al. NTRK and RET fusion–directed therapy in pediatric thyroid cancer yields a tumor response and radioiodine uptake. Journal of Clinical Investigation 2021 131. (https://doi.org/10.1172/JCI144847)
- 17↑
Groussin L, Bessiene L, Arrondeau J, Garinet S, Cochand-Priollet B, Lupo A, Zerbit J, Clerc J, & Huillard O. Selpercatinib-enhanced radioiodine uptake in RET-rearranged thyroid cancer. Thyroid 2021 31 1603–1604. (https://doi.org/10.1089/thy.2021.0144)
- 18↑
Groussin L, Clerc J, & Huillard O. Larotrectinib-enhanced radioactive iodine uptake in advanced thyroid cancer. New England Journal of Medicine 2020 383 1686–1687. (https://doi.org/10.1056/NEJMc2023094)
- 19↑
Tchekmedyian V, Dunn L, Sherman E, Baxi SS, Grewal RK, Larson SM, Pentlow KS, Haque S, Tuttle RM, Sabra MM, et al. Enhancing radioiodine incorporation in BRAF-mutant, radioiodine-refractory thyroid cancers with vemurafenib and the anti-ErbB3 monoclonal antibody CDX-3379: results of a pilot clinical trial. Thyroid 2022 32 273–282. (https://doi.org/10.1089/thy.2021.0565)
- 20↑
Groussin L, Theodon H, Bessiene L, Bricaire L, Bonnet-Serrano F, Cochand-Priollet B, Leroy K, Garinet S, Pasmant E, Zerbit J, et al. Redifferentiating effect of larotrectinib in NTRK-rearranged advanced radioactive-iodine refractory thyroid cancer. Thyroid 2022 32 594–598. (https://doi.org/10.1089/thy.2021.0524)
- 21↑
Leboulleux S, Dupuy C, Lacroix L, Attard M, Grimaldi S, Corre R, Ricard M, Nasr S, Berdelou A, Hadoux J, et al. Redifferentiation of a BRAFK601E-mutated poorly differentiated thyroid cancer patient with dabrafenib and trametinib treatment. Thyroid 2019 29 735–742. (https://doi.org/10.1089/thy.2018.0457)
- 22↑
Jafri S, & Yaqub A. Redifferentiation of BRAF V600E-mutated radioiodine refractory metastatic papillary thyroid cancer after treatment with dabrafenib and trametinib. Cureus 2021 13 e17488. (https://doi.org/10.7759/cureus.17488)
- 23↑
Hoftijzer H, Heemstra KA, Morreau H, Stokkel MP, Corssmit EP, Gelderblom H, Weijers K, Pereira AM, Huijberts M, Kapiteijn E, et al. Beneficial effects of sorafenib on tumor progression, but not on radioiodine uptake, in patients with differentiated thyroid carcinoma. European Journal of Endocrinology 2009 161 923–931. (https://doi.org/10.1530/EJE-09-0702)
- 24↑
Tesselaar MH, Crezee T, Swarts HG, Gerrits D, Boerman OC, Koenderink JB, Stunnenberg HG, Netea MG, Smit JWA, Netea-Maier RT, et al. Digitalis-like compounds facilitate non-medullary thyroid cancer redifferentiation through intracellular Ca2+, FOS, and autophagy-dependent pathways. Molecular Cancer Therapeutics 2017 16 169–181. (https://doi.org/10.1158/1535-7163.MCT-16-0460)
- 25↑
Crezee T, Tesselaar MH, Nagarajah J, Corver WE, Morreau J, Pritchard C, Kimura S, Kuiper JG, van Engen-van Grunsven I, Smit JWA, et al. Digoxin treatment reactivates in vivo radioactive iodide uptake and correlates with favorable clinical outcome in non-medullary thyroid cancer. Cellular Oncology 2021 44 611–625. (https://doi.org/10.1007/s13402-021-00588-y)
- 26↑
Tesselaar MH, Crezee T, Schuurmans I, Gerrits D, Nagarajah J, Boerman OC, van Engen-van Grunsven I, Smit JWA, Netea-Maier RT, & Plantinga TS. Digitalislike compounds restore hNIS expression and iodide uptake capacity in anaplastic thyroid cancer. Journal of Nuclear Medicine 2018 59 780–786. (https://doi.org/10.2967/jnumed.117.200675)
- 27↑
Plantinga TS, Tesselaar MH, Morreau H, Corssmit EP, Willemsen BK, Kusters B, van Engen-van Grunsven AC, Smit JWA, & Netea-Maier RT. Autophagy activity is associated with membranous sodium iodide symporter expression and clinical response to radioiodine therapy in non-medullary thyroid cancer. Autophagy 2016 12 1195–1205. (https://doi.org/10.1080/15548627.2016.1174802)
- 28↑
Steeghs EM, Kroeze LI, Tops BB, van Kempen LC, Ter Elst A, Kastner-van Raaij AW, Hendriks-Cornelissen SJB, Hermsen MJW, Jansen EAM, Nederlof PM, et al. Comprehensive routine diagnostic screening to identify predictive mutations, gene amplifications, and microsatellite instability in FFPE tumor material. BMC Cancer 2020 20 291. (https://doi.org/10.1186/s12885-020-06785-6)
- 29↑
Price EM, & Lingrel JB. Structure-function relationships in the sodium-potassium ATPase. alpha. Biochemistry 1988 27 8400–8408. (https://doi.org/10.1021/bi00422a016)
- 30↑
Zavareh RB, Lau KS, Hurren R, Datti A, Ashline DJ, Gronda M, Cheung P, Simpson CD, Liu W, Wasylishen AR, et al. Inhibition of the sodium/potassium ATPase impairs N-glycan expression and function. Cancer Research 2008 68 6688–6697. (https://doi.org/10.1158/0008-5472.CAN-07-6833)
- 31↑
Weber M, Kersting D, Riemann B, Brandenburg T, Führer-Sakel D, Grünwald F, Kreissl MC, Dralle H, Weber F, Schmid KW, et al. Enhancing radioiodine incorporation into radioiodine-refractory thyroid cancer with MAPK inhibition (ERRITI): a single-center prospective two-arm study. Clinical Cancer Research 2022 28 4194–4202. (https://doi.org/10.1158/1078-0432.CCR-22-0437)
- 32↑
García B, & Santisteban P. PI3K is involved in the IGF-I inhibition of TSH-induced sodium/iodide symporter gene expression. Molecular Endocrinology 2002 16 342–352. (https://doi.org/10.1210/mend.16.2.0774)
- 33↑
Hou P, Bojdani E, & Xing M. Induction of thyroid gene expression and radioiodine uptake in thyroid cancer cells by targeting major signaling pathways. Journal of Clinical Endocrinology and Metabolism 2010 95 820–828. (https://doi.org/10.1210/jc.2009-1888)
- 34↑
Bravo PE, Goudarzi B, Rana U, Togni Filho PT, Castillo R, Rababy C, Ewertz M, Ziessman HA, Cooper DS, Ladenson PW, et al. Clinical significance of discordant findings between pre-therapy 123I and post-therapy 131I whole body scan in patients with thyroid cancer. International Journal of Clinical and Experimental Medicine 2013 6 320–333.
- 35↑
Urhan M, Dadparvar S, Mavi A, Houseni M, Chamroonrat W, Alavi A, & Mandel SJ. Iodine-123 as a diagnostic imaging agent in differentiated thyroid carcinoma: a comparison with iodine-131 post-treatment scanning and serum thyroglobulin measurement. European Journal of Nuclear Medicine and Molecular Imaging 2007 34 1012–1017. (https://doi.org/10.1007/s00259-006-0341-x)
- 36↑
Donahue KP, Shah NP, Lee SL, & Oates ME. Initial staging of differentiated thyroid carcinoma: continued utility of posttherapy 131I whole-body scintigraphy. Radiology 2008 246 887–894. (https://doi.org/10.1148/radiol.2463061328)
- 37↑
Wang X, Zheng X, Zhu J, Li Z, & Wei T. Radioactive iodine therapy does not improve cancer-specific survival in Hürthle cell carcinoma of the thyroid. Journal of Clinical Endocrinology and Metabolism 2022 107 3144–3151. (https://doi.org/10.1210/clinem/dgac448)
- 38↑
Chindris A-M, Casler JD, Bernet VJ, Rivera M, Thomas C, Kachergus JM, Necela BM, Hay ID, Westphal SA, Grant CS, et al. Clinical and molecular features of Hürthle cell carcinoma of the thyroid. Journal of Clinical Endocrinology and Metabolism 2015 100 55–62. (https://doi.org/10.1210/jc.2014-1634)
