Introduction
Locally advanced thyroid carcinoma can involve the larynx (1,2). In such cases, partial laryngotracheal resection is often performed as surgical treatment. Successful reconstruction is required to avoid palliative stenting or permanent tracheostomy. An important aspect of laryngotracheal reconstruction is the establishment of skeletal support in order to resist airway pressure changes (3). Although there are several surgical techniques for performing laryngotracheal reconstruction, surgeons occasionally find it difficult to maintain an appropriate laryngeal and/or tracheal shape.
Anaplastic thyroid carcinoma (ATC) is a rare but highly aggressive malignant tumour that accounts for 1-2% of all thyroid malignancies (4). Although ATC is treated with a multidisciplinary approach that includes surgery, radiotherapy, and chemotherapy, its prognosis is extremely poor. Lenvatinib, a tyrosine kinase inhibitor, has been approved for use in patients with unresectable or metastatic thyroid carcinoma. The use of post-operative lenvatinib therapy has not yet been established, and further studies are required to confirm the efficacy of this therapy.
It is known that ATC may not only originate de novo but also arise as a conversion of differentiated thyroid carcinoma (5). Head and neck surgeons may sometimes encounter ATC incidentally when treating patients with locally advanced differentiated thyroid carcinomas (6).
We report a case of incidental ATC that invaded the larynx, with long-term survival with lenvatinib therapy and post-operative preservation of laryngeal function.
Discussion
The larynx not only has a complex anatomy but is also involved in multiple functions, such as breathing, speech, and swallowing. It may be directly invaded by carcinomas of the oesophagus or thyroid. It is said that 1-7% of thyroid carcinomas invade the trachea and/or larynx. Advanced thyroid carcinoma occasionally causes tracheal obstruction, leading to death (1,2). Surgical management is thought to be effective in resectable advanced thyroid carcinoma (7,8). However, it involves partial laryngotracheal resection. Our patient's tumour extended beyond the thyroid capsule, that is, from the left wing of the thyroid cartilage to the cricoid cartilage. Therefore, the laryngeal defect was reconstructed after total thyroidectomy and hemi-laryngectomy. Many authors have described the technique of laryngotracheal reconstruction (3,9-12). We used an ALT flap and rib cartilage grafts. An ALT flap is often used as material for head and neck reconstruction. However, there are few reports on its application in laryngeal reconstruction. An ALT flap has adequate size and volume to cover laryngeal defects. In our patient, we were able to use it to sufficiently compensate for a 40% defect of the larynx. It is also easy to harvest in the supine position. Moreover, the post-operative scar at the donor site is hidden behind the patient's clothes, making it relatively inconspicuous in daily life. However, follow-up of the patient's thigh condition is important. Post-operatively, older patients should undergo early rehabilitation to maintain independence in their activities of daily living.
Various materials such as the clavicle, rib cartilage, auricular cartilage, and nasal septum cartilage are used to reinforce the laryngeal lumen in case of reconstruction. We used rib cartilage because it is rigid and easy to harvest and mould. The donor site scar can be easily hidden behind the patient's clothes, similarly to that of an ALT flap. We performed laryngeal reconstruction to maintain airway patency. We vertically inserted the rib cartilage into a pocket immediately below the dermis of the skin flap. Kubo reported the effectiveness of this procedure using a forearm flap (13). As an ALT flap is soft, it is easy to mould it to the irregularly shaped larynx and place trimmed cartilage grafts inside it. Additionally, placement of the graft immediately below the dermis makes it adhere easily and helps to maintain the shape of the reconstructed larynx and trachea. Neck flexibility is also important. Movement of the cartilage pieces makes the neck more flexible. On the other hand, prevention of necrosis or leakage is important.
Although numerous techniques of laryngeal reconstruction have been reported, most of them involve stepwise procedures and palliative stenting. A one-stage procedure could reduce patient burden and help to avoid multiple surgeries. This procedure may lead to early healing of the surgical wound, which may improve patients' quality of life. Post-operative management, including monitoring for signs of infection and inflammation, is important. In our patient, post-operative computed tomography and laryngoscopy showed a reconstructed larynx with sufficient function. Twenty-six months post-operatively, the patient maintained an excellent airway and her larynx functioned adequately.
ATC is a fatal disease for which various therapeutic modalities have been unsuccessfully tried. Moreover, it has been reported that 20-50% of patients with ATC have distant metastasis at initial presentation, and the recurrence rate after treatment is nearly 40% (14,15). This worsens the prognosis. Sugitani et al (16,17) devised a prognostic index for ATC based on four unfavourable prognostic factors: Acute symptoms (duration of severe symptoms such as dysphonia, dysphagia, dyspnoea, and rapid tumour growth in <1 month), leukocytosis (leukocyte count 10,000/mm3), tumour size >5 cm, and distant metastasis. They recommended attempting multimodal treatment for patients with a prognostic index of ≤1. Our patient did not have any unfavourable prognostic factors.
Our patient experienced recurrence after laryngeal reconstruction using an ALT flap and rib cartilage grafts. While treating the recurrence, we had to focus on the condition of these flaps, which needed sufficient blood supply. Radiotherapy often damages tissues and induces inflammatory responses, such as arteritis and thrombosis in small vessels (18-20). Gessert et al (21) reported that the incidence of laryngeal chondroradionecrosis in patients with laryngeal cancer treated with radiotherapy is 2.4%. It is necessary to avoid these complications, maintain the flaps in good condition, and assume that chondroradionecrosis may occur following radiotherapy to the neck (22,23). Radiotherapy can also inhibit post-operative wound healing.
Considering these problems and the post-operative histopathological diagnosis of ATC, a multidisciplinary team consisting of medical oncologists, radiologists, and head and neck surgeons decided to avoid post-operative radiotherapy and to treat the patient with systematic administration of lenvatinib rather than local therapy. This decision led to good outcomes with respect to preservation of laryngeal function and improvement of survival.
Her condition has been maintained at 26 months after the initial treatment. She has good laryngeal function, and we will continue to regularly follow her progress.
In conclusion, one-stage laryngeal reconstruction is highly useful as a treatment for advanced thyroid carcinoma invading the larynx. This procedure could be effective in reducing patient burden and improving quality of life. The use of an ALT flap with free rib cartilage grafts resulted in maintained laryngeal function and neck flexibility. Lenvatinib may be an option for the treatment of early recurrence of ATC after reconstructive surgery with a free flap.