Reconversion therapy with lenvatinib in locoregionally advanced thyroid cancer: a case series from a Chilean public hospital

Abstract

Objective: To report our institutional experience with neoadjuvant lenvatinib as conversion therapy in patients with initially unresectable locoregionally advanced thyroid cancer.

Case reports: This retrospective case series included three patients treated at a Chilean public hospital between 2024 and 2026 with cT4a–T4b N1b M0 papillary thyroid carcinoma and invasion or loss of cleavage planes involving aerodigestive structures, vascular structures, and/or the prevertebral fascia. All patients were deemed unsuitable for upfront curative surgery and received lenvatinib 24 mg/day for 6 to 18 months, withheld 2–3 weeks before surgery. Response was assessed using RECIST 1.1 criteria and surgical resectability.

Discussion: All three patients showed tumor reduction and relevant anatomical improvement, with partial or complete recovery of cleavage planes. R0 resection was achieved in two cases and R2 resection in one, with laryngeal preservation in all patients. One patient met RECIST 1.1 criteria for partial response; the remaining patients had stable disease with meaningful surgical conversion. No major perioperative complications (Clavien-Dindo grade ≥ III) were recorded. Both patients with R0 resection received adjuvant radioiodine and remain under follow-up without evidence of structural disease; the patient with R2 resection resumed tyrosine kinase inhibitor therapy and died during follow-up. Lenvatinib may be a feasible conversion strategy in selected patients, although prognosis remains guarded when complete resection is not achieved.