Table 1.

Design of the studies analysed and patient characteristics

Reference	Year	Study design	Patient characteristics
			Total number	Age (years)		Gender, n (%)		Smoking (pack-years)	ECOG performance status, grade (%)
				Median	Range	Male	Female
[18]	2015	Retrospective	62	57	23–83	44 (71)	18 (29)	ns	ns
[19]	2012	Retrospective	26	63	41–79	23 (89)	3 (11)	ns	ns
[20]	2017	Retrospective	122	61	ns	101 (83)	21 (17)	ns	ns
[21]	2014	Prospective	51	52	36–69	48 (94)	3 (6)	ns	ns
[22]	2013	Retrospective	70	52	37–86	66 (94)	4 (6)	ns	ns
[23]	2009	Retrospective	82	53.8	11–70	69 (84)	13 (16)	ns	ns
[24]	2012	Retrospective	88	59	26–83	74 (84)	14 (16)	ns	ns
[25]	2015	Retrospective	70	65	21–91	61 (87)	9 (13)	ns	ns
[26]	2016	Retrospective	78	62	24–79	63 (81)	15 (19)	ns	0/1 (98.8)
[27]	2014	Retrospective	108	67	43–85	93 (86)	15 (14)	ns	ns
[28]	2017	Retrospective	75	59	39–80	67 (89)	8 (11)	ns	ns
[29]	2014	Retrospective	214	58	ns	175 (82)	39 (18)	ns	ns
[30]	2017	Prospective	35	67.6	50–80	32 (91)	3 (9)	ns	0/1 (100)
[31]	2016	Retrospective	69	61	39–81	61 (88)	8 (12)	>10: 40 (60.9%)	ns
[32]	2015	Retrospective	72	60	39–75	61 (85)	11 (15)	>10: 41 (56.9%)	ns
[34]	2017	Retrospective	85	66	43–79	81 (95)	4 (5)	ns	ns
[35]	2011	Retrospective	47	55.1	15–86.1	39 (83)	8 (17)	ns	0/1 (95)
[36]	2016	Prospective	86	50	40–60	80 (93)	6 (7)	ns	ns
[37]	2013	Retrospective	81	65	34–81	74 (91)	7 (9)	ns	ns
[38]	2015	Retrospective	287	64	33–89	221 (77)	66 (23)	ns	0 (63)
[39]	2014	Retrospective	100	56	27–81	86 (86)	14 (14)	ns	ns
[40]	2015	Prospective	74	56	42–73	65 (88)	9 (12)	8.75 (median)	0/1 (100)
[42]	2016	Prospective	125	59	ns	93 (74)	32 (26)	ns	0/1 (100)
[43]	2014	Retrospective	40	48	21–69	30 (75)	10 (25)	ns	ns
[44]	2017	Retrospective	76	55	42–76	68 (89)	8 (11)	ns	ns

ns not stated