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Background: Two-thirds of patients with metastatic differentiated thyroid cancer (DTC) become refractory to radioactive iodine (RAIR). The inhibition of the MAP-kinase pathway that is activated in case of BRAFV600E mutation might increase RAI incorporation into metastatic foci and reverse the RAI refractoriness. MERAIODE is a prospective multicentric open-label phase II trial, using a one-stage Fleming design, evaluating the efficacy and tolerance of trametinib (a MEK inhibitor) and dabrafenib (a BRAF inhibitor) treatment followed by the administration of RAI in metastatic RAIR DTC patients. Methods: Patients with BRAFV600E mutated RAIR metastatic DTC with RECIST progression within 18 months prior to enrollment and no lesion > 3 cm were included. A baseline rhTSH-stimulated diagnostic whole body scan (dc WBS) was performed prior to treatment initiation. Patients were treated with dabrafenib (150 mg bid) and trametinib (2 mg per day) for 42 days. At day 28, a second rhTSH-stimulated dc WBS was performed. After 35 days, a therapeutic activity of RAI (5.5 GBq) was administered. Primary endpoint was objective response rate (ORR) at 6 months according to RECIST v1.1 (central review). Patients: Among the 24 patients (mean age 67 years, 15 females) with a BRAFV600E mutated RAI refractory papillary DTC included between March 2018 and January 2020 in 8 French centers from the TUTHYREF netwok, 24 patients were treated and 21 patients were evaluable for the principal outcome at 6 months. Results: Abnormal RAI uptake was present in only 1 of the 21 patients (5%; 95%CI 0-24%) on a RAI diagnostic whole body scan (dc-WBS) performed prior to treatment initiation, in 11 patients, 11/17 (65%; 95%CI 38-86) on a dc-WBS performed 4 weeks after dabrafenib-trametinib initiation and in 20/21 (95%; 95%CI 76-100) on the post-therapeutic WBS performed after 5.5 GBq of RAI. The RECIST 6-months tumor response (central review) was partial response (PR) in 38% (95%CI 18-61), stable disease (SD) in 52% (95% CI 30-74) and progressive disease (PD) in 10% (95% CI 1-30). The median change in the sum of target lesions was -22% (range: -79 to +46) at 6 months after baseline. The 6-month fluorodesoxyglucose metabolic PET response was PR in 11/17 (65% 95%CI 38-86), SD in 4/17 (23%) (95% CI 7-50) and PD in 2/17 (12%; 95% CI 1-36). Among the 15 patients without Tg antibodies, 7 (47%) patients had a decrease of serum thyroglobulin level on T4 treatment by more than 50%All patients experienced at least one grade 1-2 adverse event, mainly asthenia, nausea, fever, diarrhea and cutaneous eruption. Nine grade 3 toxicities occurred in 6 treated patients. No grade 4-5 adverse event occurred Conclusion: The association of dabrafenib and trametinib in BRAFV600E mutated patients is effective for restoring RAI uptake and is followed by a tumor control in 90% of patients and by tumor response in 38% with limited adverse events. (PHRC 2015, NCT 03244956)

Background: The benefits of post-operative radioactive iodine (RAI) administration have not been demonstrated in patients with low risk differentiated thyroid cancer (DTC). The objective of this randomized phase III trial is to assess in low risk DTC patients the non-inferiority of a follow-up strategy as compared to a systematic adjuvant post-operative RAI administration. Methods: ESTIMABL2 is a French multicentric randomized phase III trial in patients with low-risk DTC treated with total thyroidectomy with or without prophylactic neck lymph node dissection (pT1am N0 or Nx with a sum of the diameters of tumor lesions ≥ 10mm, pT1b N0 or Nx). Two to five months after surgery, in the absence of suspicious lateral neck lymph node on ultrasonography (US), patients were randomized either to the follow-up group (FU, no RAI administration) or to the ablation group and received post-operative RAI (1.1 GBq following rhTSH stimulation). Yearly controls under levothyroxine treatment consisted in thyroglobulin (Tg) and Tg antibodies (TgAb) determinations and neck-US. The primary objective was to assess at 3 years after randomization the non-inferiority of the proportion of patients without tumor-related event in the FU group as compared to the ablation group. Non-inferiority is demonstrated if the rate of patients without event at 3 years does not differ by more than ΔL=-5%. A tumor-related event was defined by the occurrence of subsequent treatment (RAI administration or surgery) for abnormal RAI uptake on the post-therapeutic WBS or by elevated Tg or TgAb levels and/or abnormal neck US during controls. Tg levels on levothyroxine treatment were considered elevated if > 2ng/mL in the FU group and > 1ng/mL in the ablation group. TgAb were considered elevated if > the upper limit range with an increase above 50% on 2 consecutive determinations performed 6 months apart. Results: 776 low-risk DTC patients were included between 2013 and 2017 in 35 French centers within the TUTHYREF network; 83% females, mean age: 52 years, papillary TC: 96%, pT1bNx: 43.6%, pT1bN0: 37.5%, pT1amNx: 12.6%, pT1amN0: 6.3%. Among the 729 patients evaluable at 3 years after randomization, tumor-related events occurred in 18/367 patients (4.9% IC95%=[2.9; 7.6]) in the FU group and in 15/362 patients (4.1% IC95%=[2.3; 6.7]) in the ablation group. Thus, 95.1% of patients in the FU group had no event at 3 years and this percentage is not inferior from the 95.9% of patients observed in the ablation group (difference = -0.8% [95% CI:-3.3%; 1.8%]. The number of subsequent surgery and/or RAI administration was 6 (1.6% IC95%=[0.6; 3.5]) in the FU group and 9 (2.5% IC95%=[1.1; 4.7]) in the ablation group. Conclusion: this phase III trial demonstrates the non-inferiority of a follow-up strategy compared to a systematic adjuvant post-operative administration of RAI (1.1GBq following rhTSH) in low risk DTC patients (PHRC 2012; NCT01837745).

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Anaplastic thyroid cancer (ATC) is a rare lethal disease. Lenvatinib is an off-label therapeutic option for ATC in most countries, except in Japan. The aim of this multicentre retrospective survey was to analyse the efficacy and the toxicity profile of off-label lenvatinib treatment in all adults advanced ATC patients, in France. Of the 23 patients analysed (14 males; mean age 64 years), 15 were pure ATC and 8 were mixed tumors (i.e. with a differentiated or poorly differentiated component). Prior treatments included neck external beam irradiation in 74%, at least one line of chemotherapy in 22 cases, 2 lines of chemotherapy in 11 patients, other TKI in 4 cases. A central RECIST assessment was performed. Since lenvatinib initiation, median PFS was 2.7 months (95%CI; 1.9-3.5) and median OS was 3.1 months (95%CI; 0.6-5.5). OS was significantly longer in case of mixed tumors compared with pure ATC (6.3 vs 2.7 months, p=0.026). Best tumor response was partial response in 2 cases and stable disease in 7. Clinical improvement was achieved in 7 patients. Lethal adverse events occurred in 3 patients, consisting in haemoptysis in 2 cases and pneumothorax in 1 case. Among long-surviving ATC patients (> 6 months), 4 underwent biopsy of distant metastasis, revealing poorly differentiated histology; 3 of them had initial mixed ATC histology. Efficacy of lenvatinib appears limited, although pure versus mixed ATC disclose differences in disease aggressiveness and treatment response. Long-surviving ATC patients might benefit from biopsy of persistent disease, searching for histological transition or molecular target.

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