• Male/female participants who are at least 18 years of age on the day of signing informed consent with histologically confirmed diagnosis of differentiated thyroid carcinoma candidate to surgery not previously treated will be enrolled in this study.

• Patients with a risk \> 20% for persistent/recurrent disease: primary tumor \> 4 cm; multifocal papillary microcarcinoma with extra tumor extension (ETE) and known BRAF V600E mutation; clinical N1; gross ETE (macroscopic invasion of perithyroidal soft tissues); extranodal extension; expected incomplete tumour resection.

• Poorly differentiated carcinoma; Hurtle cell carcinoma.

• Patients with distant metastasis at diagnosis.

• The participant (or legally acceptable representative if applicable) provides written informed consent for the trial.

• Have measurable disease based on RECIST 1.1.

• Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1. Evaluation of ECOG is to be performed within 7 days prior to the date of allocation/randomization.

• Have adequate organ function as defined in the following table (Table 2) Specimens must be collected within 10 days prior to the start of study treatment.

• Male participants:

• A male participant must agree to use a contraception as detailed in Appendix 3 of this protocol during the treatment period and for at least 6 months (e.g. 5 terminal half-lives for pembrolizumab) after the last dose of study treatment and refrain from donating sperm during this period.

⁃ female participant is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies:

∙ Not a woman of childbearing potential (WOCBP).

‣ a WOCBP who agrees to follow the contraceptive guidance during the treatment period and for at least 4 months after the last dose of study treatment