Tracheal Replacement Using A Cryopreserved Aortic Allograft For R0 Resection In Locally Advanced Thyroid Cancer (TRITON 02 Tracheal Replacement In ThyrOid caNcer)

Airway transplantation remains a great surgical and biological challenge. This is still an unsolved problem for patients in therapeutic impasse because of major tracheobronchial lesions requiring surgical resection and airway reconstruction. Schematically, 5 principal ways of research have been explored with the use of synthetic prostheses, airway bio-prostheses, tracheal allografts, various autologous substitutes and more recently bio-engineered conduits. The lack of prospective human studies did not allow standardizing surgical approaches. Since 1997, airway bioengineering using aortic grafts as biological matrices, has been tested in our laboratory (Alain Carpentier Foundation) as a potential solution to the unsolved problem of tracheobronchial replacement. Preclinical studies showed that autologous aortic grafts, fresh and cryopreserved aortic allografts could be valuable tracheobronchial substitutes. The progressive regeneration of both epithelium and cartilage within the aortic matrices from recipient progenitor/stem cell homing permitted the restoration of new functional airways. These results allowed clinical applications in patients with extensive tracheal diseases or lung neoplasms. Recently the feasibility of this innovative approach using stented -80°C CAA was demonstrated in a prospective study including 20 patients (NCT01331863; Martinod E et al. Feasibility of bioengineered tracheal and bronchial reconstruction using stented aortic matrices. JAMA 2018;319:2212-22).

Two patients included in the series had a locally advanced thyroid cancer with a tracheal invasion. With a maximal follow-up of 2 years and 7 months, there was no complication related to surgery and no recurrence of thyroid cancer. De novo generation of cartilage within the aortic matrices allowed stent removal in both patients. Since the JAMA publication, a new prospective observational study using the same methodology has restarted on March 2019. Of the 7 new patients included, 2 had recurrent or extended thyroid cancer. Thus, 4 patients with thyroid cancer and tracheal invasion received this innovative approach of airway bioengineering using a stented cryopreserved aortic allograft. The survival of differentiated thyroid cancers is directly conditioned by a complete surgical resection and the absence of residual cancer or recurrence in the tracheal and/or esophageal wall. Locally invasive disease from differentiated thyroid cancer represents 13% to 15% of patients. T4 locally-advanced thyroid cancer includes gross extrathyroidal extension into major neck structures; T4a gross extrathyroidal extension invading subcutaneous soft tissues, larynx, trachea, esophagus or recurrent laryngeal nerve from a tumor of any size; T4b gross extrathyroidal extension invading prevertebral fascia or encasing carotid artery or mediastinal vessels from a tumor of any size. Papillary thyroid carcinoma represents the most common type of differentiated thyroid cancer associated with extrathyroidal spread. Invasion of local structures most commonly involves the strap muscles, recurrent laryngeal nerve, and trachea. Extrathyroidal spread may also affect the larynx, esophagus, and major vessels, although this is rare. Finally, 50% of all deaths are due to tracheal invasion that is poorly managed or not treated early. The incidence of these invasions is probably underestimated, reaching between 1 and 20% of patients operated for a differentiated cancer of the thyroid. Only radical surgery can improve the prognosis. No other current treatment (radiotherapy, chemotherapy) can be considered as curative. There is no recommendation for the treatment of these invasions (abstention, shaving, tracheal resection with direct anastomosis, pharyngo-laryngectomy) and therapeutic decisions are left to the discretion of the teams and their medical/surgical expertise. This study propose to evaluate the use of an innovative approach in patients with locally advanced thyroid cancer to provide a R0 surgical resection and then a better prognosis. The use of this approach could be proposed in case of incomplete resection after thyroidectomy, redo surgery, recurrence especially if there is a vocal cord paralysis and extensive tracheal invasion. This is the first known study proposing to evaluate a new approach for patients with extended thyroid cancer invading the trachea. In fact, this group of patients is usually referred to a palliative treatment including local therapy, radiotherapy and more rarely chemotherapy.