Development and validation of machine learning nomograms for predicting survival in stage IV pancreatic cancer: A retrospective study

Table 1 Baseline demographics and clinical characteristics of patients in the training and validation cohorts, n (%)

Variables	Total cohort (n = 1662)	Training cohort (n = 1163)	Validation cohort (n = 499)	P value
Age (yeas)				0.281
< 60	445 (26.77)	313 (26.91)	132 (26.45)
60-75	838 (50.42)	597 (51.33)	241 (48.30)
> 75	379 (22.80)	253 (21.75)	126 (25.25)
Sex				0.062
Female	803 (48.32)	544 (46.78)	259 (51.90)
Male	859 (51.68)	619 (53.22)	240 (48.10)
Race				0.191
White	1326 (79.78)	937 (80.57)	389 (77.96)
Black	172 (10.35)	110 (9.46)	62 (12.42)
Other	164 (9.87)	116 (9.97)	48 (9.62)
Marital status				0.935
Married	895 (53.85)	630 (54.17)	265 (53.11)
Unmarried	273 (16.43)	189 (16.25)	84 (16.83)
Divorced	429 (25.81)	297 (25.54)	132 (26.45)
Unknown	65 (3.91)	47 (4.04)	18 (3.61)
Tumor location				0.806
Head	621 (37.36)	426 (36.63)	195 (39.08)
Body	258 (15.52)	182 (15.65)	76 (15.23)
Tail	334 (20.10)	235 (20.21)	99 (19.84)
Other	449 (27.02)	320 (27.52)	129 (25.85)
T stage				0.174
T1/T2	411 (24.73)	303 (26.05)	108 (21.64)
T3	575 (34.60)	386 (33.19)	189 (37.88)
T4	337 (20.28)	236 (20.29)	101 (20.24)
TX	339 (20.40)	238 (20.46)	101 (20.24)
N stage				0.833
N0	781 (46.99)	547 (47.03)	234 (46.89)
N1	599 (36.04)	415 (35.68)	184 (36.87)
NX	282 (16.97)	201 (17.28)	81 (16.23)
Grade				0.701
Grade I/II	296 (17.81)	204 (17.54)	92 (18.44)
Grade III/IV	292 (17.57)	200 (17.20)	92 (18.44)
Unknown	1074 (64.62)	759 (65.26)	315 (63.13)
Surgery				0.672
No	1482 (89.17)	1040 (89.42)	442 (88.58)
Yes	180 (10.83)	123 (10.58)	57 (11.42)
Chemotherapy				0.706
No	686 (41.28)	484 (41.62)	202 (40.48)
Yes	976 (58.72)	679 (58.38)	297 (59.52)
Radiotherapy				0.822
No	1557 (93.68)	1088 (93.55)	469 (93.99)
Yes	105 (6.32)	75 (6.45)	30 (6.01)
Bone metastasis				0.172
No	1549 (93.20)	1077 (92.61)	472 (94.59)
Yes	113 (6.80)	86 (7.39)	27 (5.41)
Liver metastasis				0.384
No	615 (37.00)	422 (36.29)	193 (38.68)
Yes	1047 (63.00)	741 (63.71)	306 (61.32)
Lung metastasis				0.462
No	1278 (76.90)	888 (76.35)	390 (78.16)
Yes	384 (23.10)	275 (23.65)	109 (21.84)

Table 2 Univariate Cox regression analysis for cancer-specific survival and overall survival in stage IV pancreatic cancer patients

Variables	OS		CSS
	HR (95%CI)	P value	HR (95%CI)	P value
Age (years)
< 60	1 (reference)		1 (reference)
60-75	1.26 (1.10, 1.45)	0.001	1.25 (1.08, 1.44)	0.002
> 75	1.70 (1.44, 2.02)	< 0.001	1.71 (1.44, 2.03)	< 0.001
Sex
Female	1 (reference)		1 (reference)
Male	0.97 (0.87, 1.09)	0.645	0.98 (0.87, 1.10)	0.730
Race
White	1 (reference)		1 (reference)
Black	1.26 (1.03, 1.54)	0.024	1.20 (0.98, 1.48)	0.078
Other	0.88 (0.72, 1.07)	0.195	0.89 (0.73, 1.08)	0.237
Marital status
Married	1 (reference)		1 (reference)
Unmarried	1.17 (0.99, 1.38)	0.069	1.16 (0.98, 1.38)	0.079
Divorced	1.54 (1.34, 1.77)	< 0.001	1.52 (1.32, 1.76)	< 0.001
Unknown	1.72 (1.28, 2.33)	< 0.001	1.71 (1.26, 2.32)	0.001
Tumor location
Head	1 (reference)		1 (reference)
Body	1.34 (1.13, 1.60)	0.001	1.35 (1.13, 1.61)	0.001
Tail	1.20 (1.02, 1.41)	0.027	1.22 (1.03, 1.43)	0.020
Other	1.42 (1.22, 1.64)	< 0.001	1.42 (1.22, 1.65)	< 0.001
T stage
T1/T2	1 (reference)		1 (reference)
T3	0.76 (0.65, 0.89)	< 0.001	0.77 (0.66, 0.90)	0.001
T4	0.92 (0.77, 1.09)	0.339	0.93 (0.78, 1.11)	0.413
TX	1.13 (0.96, 1.35)	0.148	1.10 (0.92, 1.31)	0.288
N stage
N0	1 (reference)		1 (reference)
N1	0.96 (0.84, 1.09)	0.488	0.98 (0.86, 1.12)	0.789
NX	1.44 (1.22, 1.69)	< 0.001	1.42 (1.20, 1.68)	< 0.001
Grade
Grade I/II	1 (reference)		1 (reference)
Grade III/IV	1.68 (1.37, 2.05)	< 0.001	1.69 (1.38, 2.08)	< 0.001
Unknown	1.74 (1.48, 2.04)	< 0.001	1.72 (1.46, 2.02)	< 0.001
Surgery
No	1 (reference)		1 (reference)
Yes	0.46 (0.38, 0.56)	< 0.001	0.47 (0.38, 0.57)	< 0.001
Chemotherapy
No	1 (reference)		1 (reference)
Yes	0.33 (0.30, 0.38)	< 0.001	0.34 (0.30, 0.38)	< 0.001
Radiotherapy
No	1 (reference)		1 (reference)
Yes	0.76 (0.60, 0.97)	0.027	0.78 (0.61, 0.99)	0.040
Bone metastasis
No	1 (reference)		1 (reference)
Yes	1.10 (0.88, 1.37)	0.397	1.15 (0.92, 1.44)	0.206
Liver metastasis
No	1 (reference)		1 (reference)
Yes	1.49 (1.32, 1.68)	< 0.001	1.50 (1.32, 1.70)	< 0.001
Lung metastasis
No	1 (reference)		1 (reference)
Yes	1.02 (0.89, 1.17)	0.819	1.01 (0.88, 1.16)	0.910

OS: Overall survival; CSS: Cancer-specific survival; HR: Hazard ratio.

Table 3 Values of C-index and area under the curve of the nomogram in the training and the validation cohort

Data set	OS					CSS
	C-index (95%CI)		AUC			C-index (95%CI)		AUC
			6-month	12-month	18-month			6-month	12-month	18-month
Training set	0.727	0.711-0.743	0.801	0.775	0.787	0.727	0.711-0.743	0.800	0.774	0.785
Validation set	0.719	0.695-0.744	0.762	0.799	0.785	0.716	0.691-0.741	0.759	0.797	0.785

OS: Overall survival; CSS: Cancer-specific survival; AUC: Area under the curve.