Jérôme Clerc

Background: Subclinical hyperthyroidism grade 1 (SCH G1, TSH > 0.1 mU/L) is common in patients with thyroid unifocal autonomy (UFA) and associated with cardiovascular risks and increased mortality. While ¹³¹I radioiodine therapy (¹³¹I-RIT) effectively treats UFA, it frequently induces hypothyroidism, partly due to extra-nodular absorbed dose (AD) enhanced by residual TSH stimulation. Objective: We hypothesized that short-term LT3-induced TSH suppression at the time of RIT would promote long-term euthyroidism. Patients and Methods: A retrospective study was conducted on 95 UFA patients with SCH G1 (2001–2024). Patients underwent baseline and post-LT3 thyroid scintigraphy, and then received ¹³¹I-RIT with individualized dosimetry. Long-term bioclinical follow-up was achieved. Results: Short-term low-dose LT3 suppression caused no adverse events and significantly reduced TSH (0.45 to 0.047 mU/L). Whole-gland ¹²³I uptake decreased moderately (11.0 to 8.4%), while extra-nodular lobe uptake dropped markedly (1.77 to 0.73%) (all p < 0.0001). This focused activity on the UFA (2.5-fold increase), maintaining mean UFA AD (about 260 Gy) but reducing extra-nodular AD (61 to 37 Gy, p < 0.0001). Despite low ¹³¹I doses (mean 181 MBq), a dose–response relationship was observed: higher AD correlated with greater nodular lobe volume reduction (p < 0.033). At the 88-month follow-up, 93% of patients achieved normal thyroid function; one had persistent SCH G1, two were borderline hypothyroid, and two required LT4. Conclusions: ¹³¹I-RIT under brief LT3-induced TSH suppression induces sustained euthyroidism in SCH G1 with UFA. This simple, low-risk strategy reduces radioprotection concerns and is under evaluation to determine cardiovascular benefits.

Background. BRAF and MEK inhibitors are cornerstones of the redifferentiation strategy in metastatic radioactive iodine (RAI) resistant mutant thyroid cancers. We explored exposure-toxicity relationship for dose-limiting toxicity (DLT) onset in patients treated with dabrafenib and/or trametinib and investigated whether plasma exposure was associated with RAI reuptake. Methods. We conducted a retrospective monocentric study in which we reviewed the electronic medical records of patients treated in our institution with a tumor redifferentiation strategy, for whom plasma concentration of dabrafenib, its active metabolite hydroxy-dabrafenib, and trametinib was measured. Through concentrations (Cminpred) and total plasma drug exposure (area under the curve, AUC) of dabrafenib (AUCDAB), hydroxy-dabrafenib (AUCOHD) and trametinib (AUCTRA) were estimated. Results. Of the 22 patients treated in a redifferentiation strategy between March 2014 and December 2021, 15 were included in this study. A dabrafenib or trametinib-related DLT was experienced by 8 (62%) and 9 (64%) patients, respectively. Patients who experienced a trametinib-related DLT exhibited a significantly higher last AUCTRA than the average AUCTRA of patients who had no DLT (390, IQR: 67 vs. 215, IQR: 91 ng/mL.h-1, respectively; p = 0.008). Patients who experienced a dabrafenib-related DLT had a higher AUCDAB than observed in other patients (9265 vs. 6953 ng/mL.h-1, respectively; p = 0.09). No clinical and demographical characteristic was associated with the DLT onset. Overall, 9 of 15 (60%) patients demonstrated tumor redifferentiation. Patients in whom RAI reuptake was achieved had significant lower AUCDAB (6,990 vs. 9,764 ng/mL.h-1, p = 0.014; respectively) compared to patients who did not. Moreover, the relative exposure ratio AUCOHD/DAB was significantly higher in patients who achieved RAI reuptake (1.11 vs. 0.71, respectively; p = 0.0047). Conclusions. Our data suggest a relationship between DLT onset and trametinib plasma exposure, as well as an association between achievement of RAI reuptake and dabrafenib plasma exposure (AUC and ratio of AUCOHD/DAB). These data imply that the use of plasma drug monitoring could be helpful in guiding clinical practice in redifferentiation treatment.

Thyroid cancer is the most common endocrine cancer, with a good prognosis in most cases. However, some cancers of follicular origin are metastatic or recurrent and eventually become radioiodine refractory thyroid cancers (RAIR-TC). These more aggressive cancers are a clinical concern for which the therapeutic arsenal remains limited. Molecular biology of these tumors has highlighted a hyper-activation of the Mitogen-Activated Protein Kinases (MAPK) pathway (RAS-RAF-MEK-ERK), mostly secondary to the BRAF^V600E hotspot mutation occurring in about 60% of papillary cancers and 45% of anaplastic cancers. Therapies targeting the different protagonists of this signaling pathway have been tested in preclinical and clinical models: first and second generation RAF inhibitors and MEK inhibitors. In clinical practice, dual therapies with a BRAF inhibitor and a MEK inhibitor are being recommended in anaplastic cancers with the BRAF^V600E mutation. Concerning RAIR-TC, these inhibitors can be used as anti-proliferative drugs, but their efficacy is inconsistent due to primary or secondary resistance. A specific therapeutic approach in thyroid cancers consists of performing a short-term treatment with these MAPK pathway inhibitors to evaluate their capacity to redifferentiate a refractory tumor, with the aim of retreating the patients by radioactive iodine therapy in case of re-expression of the sodium–iodide symporter (NIS). In this work, we report data from recent preclinical and clinical studies on the efficacy of MAPK pathway inhibitors and their resistance mechanisms. We will also report the different preclinical and clinical studies that have investigated the redifferentiation with these therapies.

Metastatic thyroid cancers may dedifferentiate and become radioactive-iodine (RAI) resistant. A redifferentiating effect can be observed with inhibitors of the mitogen-activated protein kinase pathway in thyroid cancers with point mutation in oncogenes. This effect allows RAI reuptake that may lead to a therapeutic effect different from the antitumoral effect of the inhibitor. The potential redifferentiating effect of inhibitors targeting oncogenic fusion-genes was suggested by one adult and one pediatric patient using larotrectinib in NTRK -rearranged tumors. We report on three consecutive adult patients with metastatic RAI-resistant NTRK- rearranged thyroid cancer who received larotrectinib for disease progression and for whom the redifferentiating effect was examined. Larotrectinib-induced RAI reuptake in all or part of the metastatic disease for two patients and no reuptake was noted for the other patient. We demonstrate that redifferentiation of NTRK -rearranged RAI-resistant thyroid cancer with larotrectinib may exist but does not occur in all patients.

Background. Metastatic thyroid cancers may dedifferentiate and become radioactive iodine refractory. The redifferentiating effect of pharmacological drugs was reported with inhibitors of the MAPK pathway in cancer with point mutation in oncogenes. The potential redifferentiating effect of inhibitors targeting oncogenic fusion genes is only suggested by a recent and unique publication using larotrectinib in a NTRK rearranged tumor. Patients finding. Selpercatinib a highly selective RET inhibitor, was recently approved by the FDA for the treatment of RET fusion-positive lung and thyroid cancers. We had the unprecedented opportunity to observe restoration of iodine-131 uptake after selpercatinib treatment for a non-radioiodine avid metastatic thyroid cancer with a RET/PTC3 fusion gene. Conclusion. This finding of a redifferentiation effect with selpercatinib targeting a RET fusion gene, reinforces the proof of concept of this new therapeutic opportunity. Therefore, future clinical trials and treatment strategies must not forget to evaluate the redifferentiating effect of drugs targeting gene rearrangements. Furthermore, the combined approach with a targeted therapy and radioactive iodine may increase anti-tumor efficacy and minimize acquired resistance to RET inhibitors.

Although anti-CD38 monoclonal antibodies have improved the prognosis of relapsed/refractory multiple myeloma (RRMM), some patients still experience early relapses with poor outcomes. This present study evaluated the predictive value of FDG PET/CT parameters for RRMM prior to initiating anti-CD38 treatment. We included 38 consecutive RRMM patients who underwent a PET/CT scan treated at our institution at relapse. The median PFS was 12.5 months and the median OS was not reached. 42% of the patients had an initial ISS score of 1, 37% of 2, and 21% of 3. The presence of >3 focal lesions (FLs, n = 19) and the ISS score were associated with inferior PFS (p = 0.0036 and p = 0.0026) and OS (p = 0.025 and p = 0.0098). Patients with >3 FLs had a higher initial ISS score (p = 0.028). In multivariable analysis, the ISS score and >3 FLs were independent prognostic factors for PFS (p = 0.010 and p = 0.025 respectively), and combined they individualized a high-risk group with a median PFS and OS of 3.1 months and 8.5 months respectively vs. not reached for the other patients. The presence of >3 FLs on PET was predictive of survival outcomes in patients with RRMM treated using CD38 targeted therapy. Combined with the initial ISS, an ultra-high-risk RRMM population can thus be identified.

Dissemination, expressed recently by the largest Euclidian distance between lymphoma sites (SDmax), appeared a promising risk factor in DLBCL patients. We investigated alternative distance metrics to characterize the robustness of the dissemination information. In 290 patients from the REMARC trial (NCT01122472), the Euclidean (Euc), Manhattan (Man), and Tchebychev (Tch) distances between the furthest lesions, firstly based on the centroid of each lesion and then directly from the two most distant tumor voxels and the Travelling Salesman Problem distance (TSP) were calculated. For PFS, the areas under the ROC curves were between 0.63 and 0.64, and between 0.62 and 0.65 for OS. Patients with high SDmax whatever the method of calculation or high SD_TSP had a significantly poorer outcome than patients with low SDmax or SD_TSP (p < 0.001 for both PFS and OS), with significance maintained in Ann Arbor advanced-stage patients. In multivariate analysis with total metabolic tumor volume and ECOG, each distance feature had an independent prognostic value for PFS. For OS, only SDmax_Tch, SDmax_Euc _Vox, and SDmax_Man _Vox reached significance. The spread of DLBCL lesions measured by the largest distance between lymphoma sites is a strong independent prognostic factor and could be measured directly from tumor voxels, allowing its development in the area of the deep learning segmentation methods.

Article: Radioiodine therapy of thyroid autonomy - The Quarterly Journal of Nuclear Medicine and Molecular Imaging 2021 June;65(2):138-56 - Minerva Medica - Journals