Endoscopic tumor ablation for laryngotracheal intraluminal invasion secondary to advanced thyroid cancer

Surgical strategy of locally advanced differentiated thyroid cancer

Approximately 20% of patients with differentiated thyroid cancer (DTC) have direct tumor extension with invasion of the surrounding tissues such as the larynx, trachea, esophagus, or recurrent laryngeal nerve. Recent progress of molecular-targeted therapy, such as the use of tyrosine kinase inhibitors, improves survival outcome in patients with advanced DTC. However, induction of tyrosine kinase inhibitors for locally-advanced DTC has presented novel fatal adverse events including fistula in patients with infiltration toward to the trachea, pharynx and esophagus, and fatal bleeding in patients with great vessel invasion. Surgery therefore still has an important role in DTC management, particularly in local control. The surgical strategy for laryngeal/tracheal invasion, which commonly occurs by DTC, is decided according to the extension (depths and area) of the tumor. The "shave procedure" is performed when the tumor has superficially invaded the larynx/trachea. However, intra-luminal extension requires resection and reconstruction of the larynx/trachea wall. Large veins, such as the internal jugular vein and the subclavian vein, are also frequently directly invaded by DTC. Three types of jugular vein reconstruction have been advocated to avoid fatal complications according to bilateral jugular vein ligation. The majority of carotid artery invasion by DTC can be managed with tumor resection of the sub-adventitial layer without reconstruction surgery using an artificial vessel. In this review article, we examine surgery for advanced DTC, showing the surgical strategy toward DTC that has invaded the laryngotracheal, recurrent laryngeal nerve, esophagus/hypopharynx, or great vessels.

Surgery for Thyroid Cancer Invading the Trachea

Thyroid cancer invading the trachea can be asymptomatic, but when tumour invasion reaches the mucosal surface, it causes bloody sputum and dyspnoea. The treatment plan for thyroid cancer is determined based on the site, depth, and extent of the invasion. Different from tumours arising from the tracheal mucosa, in thyroid cancer, invasion begins outside the airway and progresses toward the lumen, making it difficult to accurately diagnose the extent of the invasion even with bronchoscopy. Therefore, surgeons must determine the range of resection during surgery. Invasion reaching the tracheal mucosa requires full-thickness resection and is performed using tracheal window resection combined with tracheocutaneous fistula or tracheal sleeve resection followed by end-to-end anastomosis. The airway is safely secured with window resection, but closing the tracheal stoma often requires multi-stage reconstruction. Sleeve resection is an oncologically appropriate surgical method that can be completed in one stage, although there is a risk of serious complications associated with anastomotic dehiscence. Since well-differentiated thyroid cancer progresses slowly, some degree of survival can be expected even with incomplete resection. However, when shaving is performed for tumours with deep invasion that reaches the tracheal mucosa, the residual tumour tissue continues to grow steadily and eventually leads to airway stenosis. Since reoperation for tracheal resection is difficult, radical full-thickness resection should be performed in the initial surgery. Although this surgical intervention is far more demanding for both patients and surgeons than shaving, the procedure eventually improves patient's prognosis and quality of life.

Secondary tracheal tumors: a systematic review

BACKGROUND

Secondary tracheal tumors arise from mural invasion by primary tumors in adjacent organs, metastatic lymph nodes or blood-born metastasis from distant sites. This systematic review aims to assess the presentation, management options, and clinical outcomes of these uncommon non-tracheal malignancies.

METHODS

Electronic searches of the MEDLINE database were performed to identify case series and individual case reports of tracheal invasion by primary non-tracheal tumors or metastatic disease. All English-language studies with available abstracts or articles containing primary data were included.

RESULTS

From 1978 to 2017, a total of 160 case reports or case series identified 2,242 patients with invasion of the trachea by tumors of adjacent organs (n=1,853) or by metastatic lymph nodes or hematogenous spread (n=389). Common primary sites of origin were thyroid, esophagus, and lung, and the most common presentation was metachronous (range of interval: 0 to 564 months) with dyspnea, neck mass, voice change and/or hemoptysis. A majority of patients in case reports (77.9%) and case series (66.0%) underwent resection and the most common reported operation was segmental tracheal resection. Fewer patients underwent bronchoscopic intervention (21.7%) and radiation was used in 32.2% of patients. Complications after bronchoscopic treatment included bleeding, granulation tissue, and retained secretions, while anastomotic leak, unplanned tracheostomy, and new recurrent laryngeal nerve paralysis were observed after surgical resection. The rate of 30-day mortality was low (0.01-1.80%). Median survival was higher in patients with thyroid malignancy and in patients who underwent surgical management. Follow-up time ranged from 0.03 to 183 months.

CONCLUSIONS

Patients with tracheal invasion by metastatic or primary non-tracheal malignancies should be assessed for symptoms, tumor grade, tumor recurrence and concurrent metastases to decide on optimal surgical, bronchoscopic or noninterventional therapy. Clinical experience suggests that palliative endoscopic intervention for tracheal obstruction by metastasis-bearing lymph nodes is underreported.

A new system of microwave ablation at 2450 MHz: preliminary experience

The aim of this study was to assess the feasibility of the application of the new system (Emprint Microwave Ablation System, Covidien Boulder, CO, USA) and to identify its advantages. In particular the attention was focused to the spherical ablation zone obtained and its usefulness in terms of effectiveness. The new system is composed of: a 2450 MHz generator that delivers a maximum power of 100 W, a fiberglass antenna and a pump for internally cooled antenna. Ten liver nodules (8 hepatocellular carcinomas and 2 metastasis) were percutaneously treated (mean diameter 24.9 mm, range 16-35 mm). Technical success, ablation duration time, overall procedure time and safety were registered. To define the shape of the ablation zone, multiplanar reformatting (MPR) was performed. Roundness index transverse was calculated: a value near 1 represents a more spherical ablation zone shape, and a value distant from 1 implies an oval configuration. Technical success was 100%. Mean ablation time was of 3.85 min (range 3-5 min), mean overall procedure time was 30.5 min (range 25-40 min). No major complications were recorded. Roundness index transverse presented a mean value of 0.94, meaning that a spherical shape of ablation zone was achieved. One of the most promising innovations of the new microwave technology is the spherical shape of the ablation volume that could be related with an improving of the effectiveness and safety.

Successful Treatment of Tracheal Invasion Caused by Thyroid Cancer Using Endotracheal Tube Balloon Inflation under Flexible Bronchoscopic Guidance

Tracheal invasion is an uncommon complication of thyroid cancer, but it can cause respiratory failure. A rigid bronchoscope may be used to help relieve airway obstruction, but general anesthesia is usually required. Tracheal balloon dilatation and stent insertion can be performed without general anesthesia, but complete airway obstruction during balloon inflation may be dangerous in some patients. Additionally, placement of the stent adjacent to the vocal cords can be technically challenging. An 86-year-old female patient with tracheal invasion resulting from thyroid cancer was admitted to our hospital because of worsening dyspnea. Due to the patient's refusal of general anesthesia and the interventional radiologist's difficulty in completing endotracheal stenting, we performed endotracheal tube balloon dilatation and argon plasma coagulation. We have successfully treated tracheal obstruction in the patient with thyroid cancer by using endotracheal tube balloon inflation and a flexible bronchoscope without general anesthesia or airway obstruction during balloon inflation.

Microwave tissue ablation: biophysics, technology, and applications

Microwave ablation is an emerging treatment option for many cancers, cardiac arrhythmias, and other medical conditions. During treatment, microwaves are applied directly to tissues to produce rapid temperature elevations sufficient to produce immediate coagulative necrosis. The engineering design criteria for each application differ, with individual consideration for factors such as desired ablation zone size, treatment duration, and procedural invasiveness. Recent technological developments in applicator cooling, power control, and system optimization for specific applications promise to increase the utilization of microwave ablation in the future. This article reviews the basic biophysics of microwave tissue heating, provides an overview of the design and operation of current equipment, and outlines areas for future research.