Table 1.

Main clinical characteristics of patients in the training and validation cohorts.

Variables	Training Set (N = 143)	Validation Set (N = 58)		Full Set (N = 201)
	N (%)	N (%)	p	N (%)
Sex			0.002
Female/Male	17/126 (11.9/88.1)	18/40 (31.0/69)		35/166 (17.4/82.6)
${\mathrm{Age}}^{ \S }$			0.206
<60/≥60	70/73 (49.0/51.0)	22/36 (37.9/62.1)		92/109 (45.8/54.2)
${\mathrm{Tumor} \mathrm{length}}^{ \S }$			0.222
<4 cm/≥4 cm	67/76 (46.9/53.1)	21/37 (36.2/63.8)		88/113 (43.8/56.2)
Smoking status			0.063
Yes/No	98/45 (68.5/31.5)	31/27 (53.5/46.5)		129/72 (64.2/35.8)
Alcoholism			0.520
Yes/No	73/70 (51.0/49.0)	26/32 (44.8/55.2)		99/102 (49.3/50.7)
Differentiation			0.343
Well/Moderate/Poor	17/71/55 (11.9/49.7/38.5)	8/34/16 (13.8/58.6/27.6)		25/105/71 (12.4/52.2/35.3)
Surgical approach			0.609
Left thoracotomy	49(34.3)	17(29.3)		66(32.8)
Right thoracotomy	94(65.7)	41(70.7)		135(67.2)
Lesion location			0.151
Upper/Middle/Lower	8/54/51 (5.6/58.7/35.7)	8/31/19 (13.8/53.4/32.8)		16/115/70 (7.9/57.2/34.9)
${\mathrm{pT} \mathrm{classification}}^{ †}$			0.848
${\mathrm{T}}_{1-2}$ $/{\mathrm{T}}_{3-4\mathrm{a}}$	23/120(16.1/83.9)	8/50(13.7/86.3)		31/170 (15.4/84.6)
${\mathrm{pN} \mathrm{classification}}^{ ‡}$			1.000
${\mathrm{N}}_1$ $/{\mathrm{N}}_{2-3}$	70/73 (49.0/51.0)	29/29 (50.0/50.0)		99/102(49.3/20.7)
${\mathrm{LNs} \mathrm{examined}}^{ \S }$			0.696
≥21/<21	108/35 (75.5/24.5)	46/12 (79.3/20.7)		154/47 (76.4/23.4)
Adjuvant therapy			1.00
Yes/No	43/100 (30.1/69.9)	17/41 (29.3/70.7)		60/141 (29.8/69.2)

†: pathological T classification. ‡: pathological LN classification. §: stratified by median of variables.