Construction of a novel predictive nomogram for difficult procedure of endoscopic submucosal dissection for colorectal neoplasms

Figures & data

Table 1. Characteristics of patient and lesions in the total, training and validation set.

Variable	Total (n = 368)		Training set (n = 246)		Validation set (n = 122)		p Value
	No.	%	No.	%	No.	%
Age, year, median (IQR)	64.0 (58.0–71.0)		64 (58.0–70.0)		65.0 (59.0–74.8)		.067
Procedure time, min, median (IQR)	31.0 (18.0–55.0)		31.0 (16.0–51)		30.5 (19.3–58.0)		.290
Gender							.298
Male	222	60.3	153	62.2	69	56.6
Female	146	39.7	93	37.8	53	43.3
Experience							.443
≤20 cases	114	31.0	73	29.7	41	33.6
>20 cases	254	69.0	173	70.3	81	66.4
Location							.390
Rectum	147	39.9	93	37.8	54	44.3
Left colon	106	28.8	71	28.9	35	28.7
Right colon	115	31.3	82	33.3	33	27
Diameter
<2 cm	174	47.3	123	50.0	51	41.8	.138
≥2 cm	194	52.7	123	50.0	71	58.2
Pathology							.359
Advanced neoplasia	257	69.8	168	68.3	89	73.0
non-advanced neoplasia	111	30.2	78	31.7	33	27.0
Depth^a							.076
Mucosa	317	86.1	207	84.1	110	90.2
Submucosa	50	13.6	39	15.9	11	9.0
Morphology							.153
LST	210	57.1	134	54.5	76	62.3
Others	158	42.9	112	45.5	46	37.3
Non-lifting sign							.781
Positive	34	9.2	22	8.9	12	9.8
Negative	334	90.8	224	91.1	110	90.2
Difficult lesion
Yes	197	46.5	133	54.1	64	52.5	.771
No	171	53.5	113	45.9	58	47.5
Resection method							.449
ESD	327	88.9	221	89.8	106	86.9
Conversion to piecemeal	33	9.0	19	7.7	14	11.5
ESD failure	8	2.2	6	2.4	2	1.6
En bloc resection							.245
Yes	327	90.8	221	92.1	109	88.3
No	33	9.2	19	7.9	14	11.7

IQR: Interquartile range; LST: Laterally spreading tumor; ESD: Endoscopic submucosal dissection.

^aOne lesions (0.8%) in validation set with data not available.

Table 2. Risk factors for difficult colorectal ESD procedures.

Variable	Non-difficult procedure	Difficult procedure	Univariate analysis		Multivariate analysis
	No. (%)	No. (%)	OR (95%CI)	p value	OR (95%CI)	p value
Experience of endoscopist
≤20 cases	24 (21.2)	49 (36.8)	2.163 (1.221–3.833)	.008	2.091 (1.083–4.038)	.028
>20 cases	89 (78.8)	84 (63.2)	1		1
Location
Rectum	39 (34.5)	54 (40.6)	1.385 (0.762–2.517)	.286	2.183 (1.006–4.736)	.048
Left colon	33 (29.2)	38 (28.6)	1.152 (0.609–2.176)	.664	2.475 (1.063–5.760)	.036
Right colon	41 (36.3)	41 (30.8)	1		1
Diameter
<2 cm	82 (72.6)	41 (30.8)	1		1
≥2 cm	31 (27.4)	92 (69.2)	5.806 (3.336–10.106)	<.001	6.102 (3.331–11.179)	<.001
Pathology
Non-advanced neoplasia	44 (38.9)	34 (25.6)	1		1
Advanced neoplasia	69 (61.1)	99 (74.4)	1.857 (1.079–3.196)	.025	1.762 (0.925–3.358)	.085
Morphology
Others	60 (53.1)	52 (39.1)	1		1
LST	53 (46.9)	81 (60.9)	1.763 (1.061–2.930)	.029	2.501 (1.268–4.933)	.008
Non-lifting sign
Negative	110 (97.3)	114 (85.7)	1		1
Positive	3 (2.7)	19 (14.3)	6.111 (1.759–21.234)	.004	6.569 (1.747–24.696)	.005

OR: Odds ratio; CI: Confidence interval; LST: Laterally spreading tumor.

Figure 1. The nomogram for predicting difficult colorectal ESD. LST: Laterally spreading tumor.

Figure 2. Discrimination and validation of nomogram for predicting difficult colorectal ESD. The receiver operating characteristic (ROC) curves based on the nomogram for the probability of difficult colorectal ESD in the training (A) and validation (B) sets. Calibration curves of the nomogram in the training (C) and validation (D) sets (bootstrap 1000 repetitions). Nomogram-predicted probability of difficult colorectal ESD is plotted on the x-axis and actual probability is plotted on the y-axis. The dashed 45° line represents a perfect prediction by an ideal model, and the solid line represents the performance of our nomogram, which lays closer to the dashed line, meaning a good performance of prediction. 95%CI: 95% confidence interval; AUC: Area under the curve.

Figure 3. Decision curve analysis (DCA) and clinical impact curve for the nomogram. In the DCA (A), the y-axis represents the net benefit, and the x-axis represents the threshold probability. The gray solid line represents the hypothesis that all patients had difficulty in colorectal ESD. The black solid line represents the assumption that no patients had difficulty in colorectal ESD. The red dashed line represents the nomogram, and other colored lines represent different predictors. The decision curves showed that if the threshold probability is set between 10 and 70%, using the nomogram to predict difficulty of colorectal ESD adds more net benefit than any other predictors alone. In clinical impact curve (B) the vertical axis displays number of high risk. The two horizontal axes show the correspondence between risk threshold and cost: benefit ratio. Of 1000 patients, the heavy red solid line shows the total number who would be deemed high risk for each risk threshold. The blue dashed line shows how many of those would be true positives (cases).

Data availability statement

The data that support the findings of this study are available from the corresponding author, P L upon reasonable request.