Follicular Thyroid Carcinoma with Extensive Pulmonary and Mediastinal Metastases: Long-Term Symptom Control through Sequential High-Dose IMRT in a Patient Declining Systemic Therapy

Abstract

Background: Follicular thyroid carcinoma (FTC) has a greater tendency for hematogenous spread compared with other differentiated thyroid cancers, and distant metastases may become refractory to radioactive iodine (RAI). When systemic therapy is declined or not tolerated, management becomes challenging. External beam radiation therapy (EBRT) with intensity-modulated radiotherapy (IMRT) may offer meaningful symptom control and local disease management.

Case Presentation: A 51-year-old man with metastatic FTC underwent total thyroidectomy and high-dose RAI, followed by radiologic progression with extensive pulmonary and mediastinal metastases causing dyspnea and dysphagia. The patient refused systemic therapy. High-dose mediastinal IMRT (6000 cGy/30 fractions) led to rapid symptom improvement and an 18-month symptom-free interval. Later, orbital pain and diplopia caused by a posterolateral orbital lesion were treated with IMRT (6000 cGy/30 fractions), resulting in marked relief. One year later, a painful scapular metastasis was treated with IMRT (5000 cGy/20 fractions), providing effective pain control. A follow-up whole-body staging CT performed months later during evaluation for cabozantinib initiation unexpectedly confirmed sustained thoracic response, with the largest pulmonary nodule decreasing from 45 mm to 26 mm and subcarinal lymphadenopathy shrinking from 50 × 70 mm to 38 × 21 mm. The patient remains clinically stable under cabozantinib therapy.

Conclusion: Sequential IMRT provided durable symptom control, preserved performance status, and delayed systemic therapy in this patient with RAI-refractory metastatic FTC who repeatedly declined drug treatment. IMRT may serve as a practical therapeutic strategy when systemic therapy is not feasible.