Systematic review comparing the efficacy and safety of covered and uncovered self-expanding metal stents in benign airway stenosis

Table 1 Definition of key terms

TS	TS was defined as the number of successful insertion procedures of a balloon catheter through a stenosis followed by appropriate positioning of the stent across the diseased segment and increase in tracheal diameter of the stenotic segment
CS	CS was defined as the number of patients with improved clinical symptoms pertaining to the tracheal pathology post-stent insertion
RS	RS was defined as the number of patients with a lack of abnormal pathological findings on chest X-ray investigation post-stent insertion
FS	FS was defined as the number of patients with an improved FEV1/forced vital capacity ratio or FEV1 post-stent insertion as compared to pre-stent insertion
Successful insertions1	Successful insertion of airway stent was defined as the number of insertion procedures where the stent was placed at the desired location to relieve airway stenosis
Unsuccessful insertions	Unsuccessful insertion of airway stent was defined as the number of insertion procedures where the stent could not be placed at the desired location to relieve airway stenosis
Removal success	Successful removal was defined as the number of removal procedures where airway stents were removed from tracheal lumen without immediate deterioration of patient’s clinical symptoms or restenosis of airway
Unsuccessful removal	Unsuccessful removal of airway stent was defined as the number of removal procedures where the stent could not be removed and remained lodged in the patient’s airway
Complications	Complications were defined as the number of a particular adverse stent-related clinical event occurring after insertion
Uncovered SEMS	Uncovered SEMS were defined as SEMS without any polymer coverage over the body of the stent
Covered SEMS	Covered SEMS were defined as SEMS covered with a complete polymer coverage across the entire body of the stent
Metal stent death	Metal stent death was defined as the number of patients whose death was directly caused by the insertion or removal of a SEMS

¹Successful insertions defined as achieving either technical (technical success), clinical (clinical success), radiological (radiological success), or functional (functional success) success.

CS: Clinical success; FEV1: Forced expiratory volume in one second; FS: Functional success; RS: Radiological success; SEMS: Self-expanding metal stents; TS: Technical success.

Table 2 Comparison between covered-self-expanding metal stents and uncovered- self-expanding metal stents, n (%)

	All patients with SEMS (n = 900)	Patients with covered SEMS (n = 468)	Patients with uncovered SEMS (n = 432)	P value (fisher's exact test)7
Successful insertions	1013 (93.6)1	511 (98.6)2	462 (88.2)3	< 0.001
Successful removals	435 (95.2)4	305 (95.0)5	90 (93.8)6	0.607
Stent-related deaths	1 (0.1)	0 (0.0)	1 (0.2)	0.480
Complication rate
Stent migration	88 (9.8)	58 (12.4)	30 (6.9)	0.007
Granulation tissue formation	211 (23.0)	124 (26.5)	87 (20.1)	0.027
Infection	63 (7.0)	6 (1.3)	57 (13.2)	< 0.001
Restenosis	53 (5.9)	7 (1.5)	46 (10.6)	< 0.001
Stent fracture	44 (4.9)	12 (2.6)	32 (7.4)	0.001
Bleeding	25 (2.8)	0 (0.0)	25 (5.8)	< 0.001
Pneumothorax	12 (1.3)	0 (0.0)	12 (2.8)	< 0.001
Mucus plugging	11 (1.2)	7 (1.5)	4 (0.9)	0.550
Others8	63 (7.0)	48 (10.3)	15 (3.5)	< 0.001

¹Total of 1082 metal stent insertions among patients (n = 900) with either covered or uncovered self-expanding metal stents (SEMS).

²Total of 518 insertions among patients (n = 468) with covered stents.

³Total of 524 insertions among patients (n = 432) with uncovered stents.

⁴Total of 457 metal stent removals among patients (n = 900) with either covered or uncovered SEMS.

⁵Total of 321 removals among patients (n = 468) with covered stents.

⁶Total of 96 removals among patients (n = 432) with uncovered stents.

⁷P-value showing Fisher’s exact test comparison between covered and uncovered stent insertions.

⁸Other complications include-halitosis, laryngeal oedema, bronchial obstruction, bronchomalacia, dyspnoea and a change in stent configuration.

SEMS: Self-expanding metal stents.

Table 3 Comparison between covered self-expanding metal stents, uncovered self-expanding metal stents and silicone stents, n (%)

	Patients with covered SEMS (n = 468)	Patients with uncovered SEMS (n = 432)	Silicone stent study (No. 1) (n = 263)	Silicone stent study (No. 2) (n = 63)	Silicone stent study (No. 3) (n = 58)	Silicone stent study (No. 4) (n = 75)
Successful insertions	511 (98.6)1	462 (88.2)2	181 (69.0)	-	-	70 (93.3)
Successful removals	305 (95.0)3	90 (93.8)4	117 (54.7)	-	-	49 (65.0)
Stent-related deaths	0 (0.0)	1 (0.2)	2 (0.8)	-	-	-
Stent complication rate
Stent migration	58 (12.4)	30 (6.9)	78 (18.6)5	62 (28.0)5	10 (17.2)	38 (51.0)
Granulation tissue formation	124 (26.5)	87 (20.1)	72 (17.2)5	-	-	-
Infection	6 (1.3)	57 (13.2)	-	-	14 (24.1)	-
Restenosis	7 (1.5)	46 (10.6)	24 (5.7)5	-	-	30 (40.0)
Stent fracture	12 (2.6)	32 (7.4)	-	-	1 (1.7)	-
Bleeding	0 (0.0)	25 (5.8)	-	-	-	1 (1.3)
Pneumothorax	0 (0.0)	12 (2.8)	-	-	-	5 (6.67)
Mucus plugging	7 (1.5)	4 (0.9)	-	131 (60.0)5	21 (36.2)	14 (19.0)
Others6	48 (10.3)	15 (3.5)	-	18 (8.0)5	6 (10.3)	-

¹Total of 518 insertions among patients (n = 468) with covered stents.

²Total of 524 insertions among patients (n = 432) with uncovered stents.

³Total of 321 removals among patients (n = 468) with covered stents.

⁴Total of 96 removals among patients (n = 432) with uncovered stents.

⁵Total of number of stents involved (instead of number of patients) were used to calculate complication rates. The 419 stents were inserted in patients in the silicone stent study (No. 1), 220 stents were inserted in patients in the silicone stent study (No. 2).

⁶Other complications include-halitosis, laryngeal oedema, bronchial obstruction, bronchomalacia, dyspnea, and a change in stent configuration.