Reconstruction of esophageal fistula induced by lenvatinib in thyroid cancer using deltopectoral flap.

Lenvatinib, a multi-target tyrosine kinase inhibitor, has demonstrated efficacy in the treatment of various solid tumors, including thyroid cancer. However, life-threatening complications such as fistula formation have been observed in some cases. We report the case of a 47-year-old woman who developed an esophageal fistula following lenvatinib treatment for recurrent thyroid cancer. The patient initially underwent limited resection of the muscular layer of the cervical esophagus and preservation of the mucosa, followed by prophylactic radiotherapy because of inadequate surgical margins. Locoregional and pulmonary metastases developed 8 months postoperatively, and lenvatinib therapy was initiated at a dose of 24 mg. Subsequently, a fistula developed from the esophagus to the cervical skin. Esophageal fistula reconstruction was performed using a deltopectoral (DP) flap. Lenvatinib was resumed at a reduced dose of 14 mg two months after reconstruction. At 18 months after resuming lenvatinib, progression-free survival and adequate oral intake were achieved. The success of the DP flap reconstruction in this case highlights its potential as a durable solution for esophageal fistulas in patients receiving lenvatinib treatment. The robust blood supply provided by the DP flap may counteract the antiangiogenic effects of lenvatinib, thereby enabling continued treatment for locoregional recurrence.