Malignant Airway Obstruction: Brachytherapy, Cryotherapy, Argon Plasma Coagulation, and Stents

James N. Allen, M.D.

Division of Pulmonary and Critical Care Medicine

I. Causes of large airway obstruction:

A. Malignant obstruction

B. Non-malignant strictures

C. Tracheomalacia

D. Tracheo-esophageal fistula

E. Kyphoscoliosis with airway compression

F. Extrinsic Compression

II. When to intervene?

A. Indications (symptoms):

1. Limiting dyspnea

2. Post-obstructive pneumonia

3. Symptomatic hypoxemia

4. Failure to wean from the ventilator

*Remember: just because you can do an airway procedure does not mean that you should do an airway procedure

III. Brachytherapy:

a) Technique:

(1) A bronchoscopic catheter is placed across the obstructing tumor

(2) A radioactive iridium source is advanced through the catheter

(3) The catheter is withdrawn after approximately 15 minutes

(4) The radiation delivered is high potency but has a relatively shallow depth of penetration (approximately 1 cm)

b) Indications:

(1) If symptoms from the obstruction are mild to moderate

(2) In general, used after a full course of external beam radiation or concurrent with external beam radiation

(3) If the airway is completely occluded and the patient can withstand the approximately 2 weeks prior to brachytherapy-induced tumor regression (often a problem in patients on mechanical ventilators)

(4) In short bronchial segments where a stent will likely overhang otherwise patent bronchi (eg, right upper lobe bronchus)

c) Contraindications:

(1) Previous maximal brachytherapy to the area

d) Complications:

(1) Fibrinous obstruction

(2) Bleeding

(3) Fistula formation

IV. Cryotherapy

a) Technique:

(1) Requires a 2.6 mm working channel through a fiberoptic bronchoscope

(2) Nitrous oxide cools the cryotherapy probe tip to -40°C

(3) One to three 1 minute freeze-thaw cycles

(4) Can be used for malignant or benign strictures

(5) Provides excellent hemostasis and permits forceps debridement of obstructing tumors after cryotherapy

b) Advantages:

(1) Safer than laser

(2) May be able to cure some carcinoma in situ

(3) Equipment is less expensive than laser equipment

(4) Can be performed at the bedside in the ICU

c) Disadvantages:

(1) Does not provide immediate effect

(2) May require multiple treatments

V. Argon plasma coagulation

a) Technique:

(1) High voltage electrical energy transmitted vis an arc of plasma energy associated with a stream of argon gas

(2) Probe passed through the bronchoscope

b) Advantages:

(1) Excellent hemostasis

(2) Short length of argon plasma energy which minimizes collateral tissue damage

(3) Immediate effect

c) Disadvantages:

(1) High cost of disposable probes

(2) Need to avoid high oxygen concentrations because of risk of fire

(3) Relativelly shallow depth of penetration (approximately 3 mm)

VI. Stents:

a) When should they be used?

(1) If the patient has respiratory failure from airway obstruction

(2) If the patient has non-resolving post-obstructive pneumonia

(3) If the patient has impending obstruction of a major bronchus that would be life-threatening if it became completely occluded during the 3 week brachytherapy course

(4) Impending obstruction of the trachea

(5) If the patient has obstruction after completing a course of brachytherapy

(6) If the patient has malignant obstruction and refuses or cannot undergo brachytherapy

(7) If brachytherapy for malignant obstruction is not available

b) Types of stents

A. Silicone stents:

1. Advantage:

a) Removable

2. Disadvantage:

a) Reduce intralumenal diameter

b) Retained secretions

(1) Potential for life-threatening airway obstruction

(2) Potential for recurrent infections

(3) Hallatosis frequent

c) Migration

d) Must be placed with a rigid bronchoscope (except Rusch-Y)

(1) Airway should generally be pre-dilated with rigid scope prior to stent placement

3. Types:

a) Rüsch Y (Rüsch Inc., Duluth, GA)

(1) Combined tracheal/bronchial stent with a "Y"biforcation to permit simultaneous stenting of the trachea and both main bronchi

(2) Has the advantage of a silicone body with stainless steel rings which simulate the tracheal rings

(3) In general, "Y" stents are less likely than straight stents to migrate proximally

(4) Can be placed with a laryngoscope using fluoroscopic guidance

b) Hood bronchial stent (Hood Laboratories, Pembroke, MA)

(1) Sialastic stent suitable for areas of tight stenosis where proximal migration is unlikely

c) Dumon bronchial stent (Bryan Corp., Woburn, MA)

(1) Sialastic stent with struts that project into the bronchial wall to help anchor the stent in place

d) Montgomery T-tube

(1) One of the first stents available clinically

(2) Best suited for upper or mid-tracheal lesions

4. Ohio State University experience using Rüsch-Y stents in respiratory failure

a) 6 patients with acute respiratory failure and unable to wean from the ventilator

b) Underlying illness: malignant obstruction (3 patients), tracheobronchial malacia (2 patients), tracheo-esophageal fistula due to malignancy (1 patient)

c) Outcome: 4/6 weaned from the ventilator, 1/6 discharged with chronic home ventilator, 1/6 died of underlying malignancy

B. Metal stents:

1. Advantages:

a) Permanent

b) Generally become covered with new epithelial tissue consisting of ciliated pseudostratified epithelium within 3-4 months

c) Can be placed with a flexible bronchoscope

d) Do not require general anesthesia

e) Can be done on an outpatient basis

f) Can be done on ventilated patients in the ICU

2. Disadvantages:

a) Permanent

b) Can cause compression necrosis if over distended

c) If they collapse, they can cause airway obstruction

d) Tumor can re-grow through the stent with recurrent obstruction

3. Types of metal bronchoscopic stents:

a) Wallstent (Schneider, Inc., Minneapolis, MN)

(1) Soft and flexible

(2) Consist of a woven mesh of stainless steel

(a) Currently available model consists of 20 braided stainless steel filaments

(b) A polyurethane covered metal mesh stent is also available to prevent turmor growth through the stent mesh

(3) Self-expanding to a set maximal diameter as an outer covering sheath is withdrawn

(4) Do not require a balloon dilation (although this can be helpful in some circumstances)

b) Palmaz (Johnson & Johnson Interventional Systems, Warren, NJ)

(1) Very stiff

(2) Metal stent which is loaded over a balloon which is used to distend the stent to a desired diameter

(3) It can be irreversibly deformed and crushed with the force of coughing resulting in airway obstruction

c) Ultraflex (Boston Scientific, Watertown, MA)

(1) Soft and flexible

(2) Made of a single woven nitinol wire (nitinol = titanium + nickel; nitinol is safe for patients undergoing MRI) - available either as bare wire stent or as a covered stent

(3) Self-expanding to a maximum set diameter

(4) Requires initial placement of a guidewire via a flexible bronchoscope

(5) Does not require balloon dilation

(6) Has a nylon braid at either end of the stent which can be grasped by transbronchial forceps for easy re-positioning of the stent after deployment

(7) A major advantage over the Wallstent is that as it expands, it does not shorten, thus making ideal positioning of the proximal and distal ends of the stent easier

c) Placement of metal stents:

A. Stent selection

1. Of the currently available metal stents, the Ultraflex and the Wallstent are probably the safest, easiest to place, and least likely to migrate or perforate the airway. These are the stents that we use most commonly at Ohio State

2. The decision of whether to use an Ultraflex or a Wallstent requires experience with both devices. The Ultraflex is more forgiving for the less experienced operator but the Wallstent anchors itself into position better than the Ultraflex. The Wallstent also has greater radial force than the Ultraflex. At OSU, we require a minimum of 10 supervised stents for credentialling purposes.

B. Pre-stent placement assessment:

1. Normal bronchial anatomy:

a) Trachea = 60 - 90 mm in an adult (intrathoracic component only)

(1) Average transverse diameter:

(a) Women = 15.2 ± 1.4

(b) Men = 18.2 ± 1.2

b) Left mainstem bronchus about 45 mm

c) Right mainstem bronchus about 25 mm

d) Right upper lobe bronchus about 10 mm

e) Bronchus intermedius about 20 mm

f) Right middle lobe about 12 mm

g) Left upper lobe about 9 mm

h) Normal bronchial diameters range from 8-12 mm for main and lobar bronchi

2. Radiographic assessment:

a) Plain chest radiographs

(1) Occasionally sufficient

b) Helical CT

(1) Measure contralateral analagous bronchus

(2) Determine if the lesion is calcified (ie, firm and unlikely to open without balloon dilation)

(3) Measure the diameter of the bronchus below and above the area of obstruction

(4) Measure the distance between the desired distal end of the stent and desired proximal end of the stent

3. Bronchoscopic assessment:

a) Visualize location of lesion relative to patent bronchi

b) Determine if lesion is pliable and soft

c) If bronchoscope can be forced beyond the lesion, determine the length of the lesion and the length between patent bronchi by measuring the length of bronchoscope withdrawn as it is pulled back from beyond the lesion

C. Stents are available in multiple sizes:

1. 5 - 24 mm diameter by 20 - 90 mm length

2. Typical selections:

a) Bronchus intermedius: 8-10 x 20 mm

b) Right mainstem bronchus: 10-12 x 20 mm

c) Left mainstem bronchus: 10-12 x 20-42 mm

d) We generally keep 8 x 20, 10 x 20, 12 x 20, 12 x 40, 16 x 60, and 18 x 60 mm stents in stock since these are the most frequently used stents in our patient population

3. If in doubt about appropriate length, use a shorter length - a second stent can always be placed later

4. Catheter sizes (in which Wallstents are loaded for deployment) are measured in French scale

a) 1 French = 0.33 mm

b) Transbronchoscopic stent catheters are generally 7 French (2.3 mm) and thus require at least a 2.6 mm working channel in the bronchoscope for passage

D. Placement issues:

1. Positioning

a) Fluoroscopy must be used

b) Mark desired distal position of airway to be stents with a radio-opaque marker taped to the chest (eg, a paper clip) using simultaneous fluoroscopy and bronchoscopy

2. If airway is completely or near completely occluded, use a guidewire to feed the stent through

a) Flexible tipped guidewires are preferable since they less likely to perforate the bronchus

b) Need ³ 200 cm guidewire (generally .035) to extend the length of the stent and the lesion in front of it

c) Guidewires are unnecessary for the smaller Wallstents, especially when being placed in patients with a partially patent airway

3. If airway if completely or near completely occluded, consider initial balloon dilation prior to stent placement

a) Angioplasty balloons can be fed over the same guidewire used to feed the stent over

E. Stent deployment (Wallstent):

1. First pass the stent catheter beyond the position of the obstruction

2. The stent is deployed slowly by sliding the the plastic sheath backward over the metal guide tube

3. Initially partially deploy stent (allow about 1/4 to 1/3 of the length of the stent to expand) 4-5 mm beyond the desired distal final position of the stent and "snug" the stent up so that the distal end to the stent coincides with the location in the bronchus previously marked with the paperclip

4. Once the distal end of the stent is appropriately positioned, slowly deploy the remaining, proximal end of the stent

5. When placing a stent in the trachea

a) If an endotracheal tube is present, it must be withdrawn up to a position well above the anticipated proximal end of the deployed stent so as to not interfer with the expansion of the stent

b) Start the deployment in the right mainstem bronchus and pull the partially deployed distal end of the stent into the carina so that it is appropriately positioned in the lower trachea, then fully deploy the stent

6. Inadequate deployment

a) Results in a stent that is too narrow and too long (for Wallstents)

b) Post-deployment balloon dilatation can result in widening of the stent diameter and shortening of the stent length to appropriate size

F. Stent deployment (Ultraflex):

1. First pass a guidewire through the bronchoscope across the obstruction; remove the bronchoscope and pass the stent catheter over the guidewire beyond the position of the obstruction

2. The stent is deployed slowly by pulling back on the ring on the distal end of the stent catheter; this unwraps the thread wrapped around the stent and permits expansion of the stent

3. For "distal release" stents: initially partially deploy stent (allow about 1/4 to 1/3 of the length of the stent to expand) 4-5 mm beyond the desired distal final position of the stent and "snug" the stent up so that the distal end to the stent coincides with the location in the bronchus previously marked with the paperclip. Once the distal end of the stent is appropriately positioned, slowly deploy the remaining, proximal end of the stent.

4. For "proximal release" stents: initially partially deploy the sent and insure that the fully expanded proximal end of the stent is flush with the radio-opaque paper clip by flouroscopy (an alternative is to re-insert the bronchoscope and directly visualize the proximal end of the stent to verify the position). Once the proximal position of the stent is appropriately positioned, slowly deploy the remaining, distal end of the stent.

5. When placing a stent in the trachea

a) If an endotracheal tube is present, it must be withdrawn up to a position well above the anticipated proximal end of the deployed stent so as to not interfer with the expansion of the stent

b) Start the deployment in the right mainstem bronchus and pull the partially deployed distal end of the stent into the carina so that it is appropriately positioned in the lower trachea, then fully deploy the stent

6. Inadequate deployment

a) Results in a stent that is too narrow and too long (for Wallstents)

(1) Post-deployment balloon dilatation can result in widening of the stent diameter and shortening of the stent length to appropriate size

b) Results in a stent which is too high or too low in the desired airway (for Wallstents or Ultraflex stents)

(1) For Ultraflex stents, the nylon thread wrapped around the proximal and distal ends of the stent can be grasped with transbronchial forceps and used to "drag" the stent to a more proximal or distal position

(2) For Wallstents, the stent must often be removed with rigid bronchoscopy so as to not injure the airway and larynx from the sharp protruding bare wires at either end of the stent

d) Complications of metal stents:

A. Cough

1. Fairly uncommon with metal stents

2. Can occur if the stent selected is too small for the airway lumen

B. Obstruction of bronchial orifaces

1. Often this is an asymptomatic condition although it can on occasion cause:

a) Localized wheezing as air passes through the mesh of the stent

b) Impaction by secretions wtih dyspnea due to obstruction of the airway lumen

c) Pneumonia

2. If the stent is so long that it overhangs an otherwise patent bronchus (eg, a right mainstem stent extends 6 mm into the trachea and obstructs the left mainstem bronchus) there are several options for treatment:

a) Use transbronchial scissors to make a longitudinal cut in the stent and allow the stent to expand open (only on Wallstents)

(1) In the example, make a 6 mm longitudinal cut in the proximal left wall of the stent so that the left mainstem bronchus becomes patent

(2) This is the easiest option for most pulmonologists but does require some degree of extra skill in transbronchial scissor technique

b) Remove the stent and replace it with a shorter stent

(1) Stent removal is difficut if even possible at all once the stent has become epithelialized; Ultraflex stents can be removed easier than Wallstents

(2) Wallstents require use of rigid bronchoscope for attempted removal

C. Secretion retention

1. Generally occurs if stent is obstructing a bronchial oriface or if a covered wire stent is used

D. Tumor regrowth through stent mesh with recurrent obstruction

1. Can be avoided by placement of a covered stent although growth through the wire mesh at either the proximal or distal ends of the stent can occur

E. Proximal migration of stent

1. More common with fixed diameter stents (eg, Palmaz) or if too small a stent was initally selected

2. More common when stent placement is followed by radiation and/or chemotherapy with tumor regression

F. Obstruction of stent by bent wires

1. Can occur due to suction catheters, etc

2. Wires can be bent back into appropriate position by transbronchial biopsy forceps

G. Erosion into nearby blood vessels

1. More common with rigid metal stents (eg, Palmaz)

2. Stents should be used cautiously if at all when airway obstruction is due to compression by a vessel

e) The Ohio State Stent Experience (100 metal stents placed through April, 2000):

A. Complications:

Granulation tissue (15%)

Most common in tracheal stents placed for benign conditions, especially if there is ongoing injury/irritation to the trachea (eg, tobacco smoke, GE reflux)

Stents requiring revision (10%)

Scissors

Unbent using forceps

Required removal (8%)

Malpositioned (10%)

Migrated (5%)

Bent (2%)

Halitosis (4%)

B. Outcome:

Total improved (84%)

Decreased dyspnea (87%)

Resolved post-obstructive pneumonia (81%)

Weaned from mechanical ventilation (63%)

C. Location of stents:

Trachea (35%)

Left mainstem (24%)

Bronchus intermedius (17%)

Right mainstem (14%)

Right middle lobe (3%)

Left lower lobe (3%)

Right lower lobe (3%)

D. Conclusions:

1. Stents most likely to be of clinical benefit when obstruction is in:

a) trachea

b) left or right mainstem bronchus

c) bronchus intermedius

2. The Palmaz stent is very rigid and can become bent or migrate after placement which strongly limits its use

3. The Wallstent maintains excellent radial force which when coupled with the exposed metal prongs at the proximal and distal ends results in the stent being securely fixed in position. However, the tendency of the stent to remain longer than anticipated if it is inompletely deployed can result in the stent overhanging bronchial orifaces. It is very difficult (and often impossible) to remove after placement.

4. The Ultraflex stent maintains good radial force but lacks the exposed metal prongs at the ends to rigidly lock the stent in place. Unlike the Wallstent, it can be repositioned or removed relatively easily using the flexible bronchoscope making it a more forgiving device.

VII. Personal preferences for malignant airway obstruction:

a) Use external beam radiation for initial management of mild-moderate symptoms of malignant obstruction

b) Use brachytherapy, cryotherapy, or argon plasma coagulation for patients failing external beam radiation or for patients in whom external beam radiation is contraindicated

c) Use stents for patients with severe symptoms of malignant obstruction and for patients who have already had brachytherapy and/or cryotherapy

last updated January 22, 2004