Lenvatinib treatment strategy for thyroid carcinoma with malignant pleurisy: a case report.

Background: Although lenvatinib is effective for unresectable thyroid carcinoma, it may cause adverse events owing to rapid tumor shrinkage or necrosis. Pneumothorax during lenvatinib therapy is rare. However, once it occurs, it can become a refractory and fatal complication. Herein, we report two cases of thyroid carcinoma with malignant pleurisy treated with lenvatinib and discuss treatment strategies to prevent pneumothorax.

Case description: The first case involved a 78-year-old male with papillary thyroid carcinoma and malignant bilateral pleural effusion. He underwent pleurodesis with talc for the left pleural effusion due to respiratory distress, and lenvatinib therapy was initiated. Forty days after lenvatinib therapy, the patient developed a right pneumothorax and underwent surgery for a prolonged air leak. However, the left pneumothorax was prevented by pleurodesis. During surgery, the visceral pleura was fragile, and repair of the pulmonary fistula was difficult. Pathological examination revealed an anaplastic carcinoma in the visceral pleura. The air leak disappeared 20 days after surgery; however, the patient died 22 days after surgery due to progression of the underlying disease. The second case involved a 65-year-old female with a poorly differentiated thyroid carcinoma and lung metastasis. She underwent ablation with 30 mCi ¹³¹I after total thyroidectomy, and there was no accumulation in the metastatic sites. Chest computed tomography (CT) revealed the progression of malignant pleurisy in the right thoracic cavity, and iodine-resistant disease was confirmed. She was treated with lenvatinib after talc pleurodesis and showed good progress without any adverse events.

Conclusions: The presence of malignant pleurisy results in a risk of developing lenvatinib-associated pneumothorax. Therefore, pleurodesis should be considered before lenvatinib therapy for thyroid carcinomas with malignant pleurisy.