基于随机森林算法的胰腺癌术后预测模型构建

doi:10.13481/j.1671-587X.20220220

摘要/Abstract

摘要： 目的

通过随机森林算法构建胰腺癌患者术后５年生存情况预测模型，为胰腺癌患者术后预后评估提供指导。

方法

利用美国国立癌症研究所监测、流行病学和结果数据库（SEER）收集符合本研究要求的42 618条胰腺癌患者及其预后数据，经过数据筛选最终纳入4 020条患者信息。将研究对象随机分为训练集和测试集，采用χ^２检验、多因素Logistic回归分析和随机森林变量重要性排名进行特征变量选择；利用合成少数样本过采样技术（SMOTE）将训练集调整为平衡数据集；基于平衡后数据集利用随机森林算法构建预测模型；利用测试集，基于G-mean指数、灵敏度、特异度和受试者工作特征（ROC）曲线下面积（AUC）4个评价指标，分别与Logistic回归分析、支持向量机、决策树和人工神经网络算法进行比较，对预测模型做出评价。

结果

原始训练集中包含2 814个样本，其中生存时间≥5年的患者有196例，占比约1/13，是不平衡数据集，经过SMOTE方法调整后获得平衡数据集，二分类样本数量基本达到平衡。最终纳入模型的变量有年龄、种族、肿瘤原发部位、肿瘤分化程度、是否放疗、T分期、N分期、婚姻状况、肿瘤大小和淋巴结阳性比率。基于随机森林算法构建的胰腺癌患者术后预测模型G-mean指数为0.830，AUC为0.833［P<0.05，95%置信区间（CI）（0.784，0.876）］，优于Logistic回归分析、支持向量机、决策树和人工神经网络。

结论

基于随机森林算法构建的胰腺癌术后预测模型对胰腺癌患者术后５年生存情况的预测性能优于其他常见机器学习方法，能够为临床医生改善胰腺癌患者的预后和生存状况提供依据。

关键词: 胰腺肿瘤, 随机森林算法, 预测模型, 预后, 模型比较

Abstract: Objective

To establish a prediction model of 5-year survival after operation in the pancreatic cancer patients by random forest algorithm， and to provide guidance for prognosis evaluation after operation in the pancreatic cancer patients.

Methods

Surveillance， Epidemzology，and End Results Program（SEER） database was used to collect 42，618 data of the pancreatic cancer patients and their prognosis which met the requirements of this study. After data screening， 4，020 data of the patients were finally included. The subjects were randomly divided into training set and test set， and the characteristic variables were selected by means of χ^２test， multivariate Logistic regression analysis and random forest variable importance ranking； Synthetic Minority Oversampling Technique（SMOTE） was used to adjust the training set to a balanced data set； Based on the balanced data set， the prediction model was constructed by using random forest algorithm； Using the test set， based on the four evaluation indexes of G-mean index， sensitivity， specificity， and area under receiver operating characteristic（ROC） curve（AUC）， the prediction model was evaluated by comparing with logistic regression analysis， support vector machine， decision tree and artificial neural network algorithm.

Results

The original training set contained 2，814 samples， of which 196 patients with a survival time ≥5 years， accounting for about 1/13. It was an unbalanced data set. The balanced data set was obtained after adjustment by SMOTE， and the number of two classification samples was basically balanced. The final variables included in the model were age， race， primary tumor location， tumor differentiation degrees， radiotherapy or not， T stage， N stage， marital status， tumor size and lymph node positive rate. The G-mean index of pancreatic cancer prediction model based on random forest algorithm was 0.830， and the AUC was 0.833， which was better than Logistic regression analysis， support vector machine， decision tree and artificial neural network.

Conclusion

The prediction performance of prediction model of pancreatic cancer based on random forest algorithm is better than other common machine learning methods in predicting the 5-year survival rate of patients with pancreatic cancer. It can provide a basis for clinicians to improve the prognosis and survival of patients with pancreatic cancer.

Key words: Pancreatic neoplasms, Random forest algorithm, Prediction model, Prognosis, Model comparison

中图分类号:

R735.9

李承圣,包绮晗,郝晓燕,潘庆忠,王素珍,石福艳. 基于随机森林算法的胰腺癌术后预测模型构建[J]. 吉林大学学报(医学版), 2022, 48(2): 426-435.

Chengsheng LI,Qihan BAO,Xiaoyan HAO,Qingzhong PAN,Suzhen WANG,Fuyan SHI. Establishment of prediction model for postoperative pancreatic cancer based on random forest algorithm[J]. Journal of Jilin University(Medicine Edition), 2022, 48(2): 426-435.

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Variable	Assignment	Records in SEER database	Number	Percentage(η/%)
Age(year)	1	≤49	253	6.3
	2	50－59	789	19.6
	3	60－69	1 414	35.2
	4	70－79	1 180	29.4
	5	≥80	384	9.6
Gender	1	Female	1 962	48.8
	2	Male	2 058	51.2
Race	1	Black	413	10.3
	2	White	3 263	81.2
	3	Other	344	8.6
PrimarySite	1	Pancreatic head	3 063	76.2
	2	Pancreatic body	274	6.8
	3	Pancreatic tail	355	8.8
	4	Pancreatic overlap	179	4.5
	5	Other	149	3.7
Grade	1	GradeⅠ	344	8.6
	2	GradeⅡ	2 022	50.3
	3	GradeⅡ	1 619	40.3
	4	GradeⅣ	35	0.9
Chemotherapy	1	No	1 157	28.8
	2	Yes	2 863	71.2
Radiotherapy	1	No	2 759	68.6
	2	Yes	1 261	31.4
Number of lymph node dissections	1	0－3	180	4.5
	2	≥4	3 840	95.5
T stage	1	T1	154	3.8
	2	T2	354	8.8
	3	T3	3 296	82.0
	4	T4	216	5.4
N stage	1	N0	1 062	26.4
	2	N1	2 958	73.6
M stage	1	M0	3 785	94.2
	2	M1	235	5.8
Marital status	1	Married	2 604	64.8
	2	Single	514	12.8
	3	Other	902	22.4
Tumor size(l/mm)	1－540	－	－	－
Lymph node positive ratio	0－1	－	－	－
“－”:No data.

Variable	Training set （n=2 814）	Test set （n=1 206）	Statistic	P
Age(year)			Z=－0.553	0.580
≤49	168	77
50－59	561	210
60－69	990	441
70－79	821	375
≥80	274	103
Gender			χ^２=0.088	0.767
Female	1 388	601
Male	1 426	605
Race			χ^２=1.233	0.540
Black	285	135
White	2 278	970
Other	251	101
Primary site			χ^２=4.405	0.354
Pancreatic head	2 145	938
Pancreatic body	192	78
Pancreatic tail	247	110
Pancreatic overlap	124	37
Other	106	43
Grade			Z=－0.234	0.815
GradeⅠ	246	110
GradeⅡ	1 433	612
GradeⅢ	1 111	474
GradeⅣ	24	10
Chemotherapy			χ^２=0.011	0.915
No	812	346
Yes	2 002	860
Radiotherapy			χ^２=0.658	0.417
No	1 922	808
Yes	892	398
Number of lymph node dissections			χ^２=0.262	0.609
0－3	125	58
≥4	2 689	1 148
T stage			Z=－0.991	0.322
T1	105	40
T2	259	97
T3	2 293	1 004
T4	157	65
N stage			χ^２=0.193	0.661
N0	728	320
N1	2 086	886
M stage			χ^２=0.683	0.409
M0	2 646	1 142
M1	168	64
Marital status			χ^２=4.613	0.100
Married	1 826	763
Single	352	181
Other	636	262
Tumor size	2 814	1 206	Z=－0.002	0.998
Lymph node positive ratio	2 814	1 206	Z=－0.257	0.797

Variable	Training set		Variable	Training set
Variable	Statistic	P	Variable	Statistic	P
Age（year）	Z=－2.841	0.004	Chemotherapy	χ^２=11.289	0.001
≤49			No
50－59			Yes
60－69			Radiotherapy	χ^２=11.033	0.001
70－79			No
≥80			Yes
Gender	χ^２=0.118	0.731	Number of lymph node dissections	χ^２=0.064	0.800
Female			0－3
Male			≥4
Race	χ^２=0.066	0.968	T stage	Z=－5.501	<0.001
Black			T1
White			T2
Other			T3
Primary site	χ^２=1.025	0.906	T4
Pancreatic head			N stage	χ^２=110.965	<0.001
Pancreatic body			N0
Pancreatic tail			N1
Pancreatic overlap			M stage	χ^２=4.387	0.340
Other			M0
Grade	Z=－12.723	<0.001	M1
GradeⅠ			Marital status	χ^２=2.160	0.340
GradeⅡ			Married
GradeⅢ			Single
GradeⅣ			Other
			Tumor size	Z=－6.460	<0.001
			Lymph node positive ratio	Z=－10.771	<0.001

Variable	Training set
Variable	B	Std.Error	Wald	P	Exp(B)	95% Exp(B)
Grade	－0.425	0.120	12.599	<0.001	0.654	(0.517,0.822)
Chemotherapy	0.597	0.211	7.982	0.005	1.816	(1.201,2.784)
Radiotherapy	0.335	0.169	3.937	0.047	1.398	(1.004,1.947)
T stage	－0.268	0.119	5.048	0.025	0.765	(0.606,0.966)
N stage	－0.595	0.214	7.720	0.005	0.552	(0.363,0.839)
Tumor size	－0.023	0.006	12.570	<0.001	0.978	(0.965,0.990)
Lymph node positive rate	－3.980	0.927	18.432	<0.001	0.019	(0.003,0.115)

SMOTE dataset	Perc.over	Perc.under	Negative sample size	Positive sample size	Class.error(－)	Class.error(+)	OOB error(%)
Training set	－	－	2 618	196	0.001	0.995	7.00
1	1 300	100	2 548	2 744	0.082	0.122	10.26
2	1 200	100	2 352	2 548	0.085	0.113	9.94
3	1 100	100	2 156	2 352	0.089	0.115	10.27
4	1 000	100	1 960	2 156	0.102	0.122	11.20
5	900	100	1 764	1 960	0.109	0.132	12.11
6	800	100	1 568	1 764	0.116	0.128	12.24
7	700	100	1 372	1 568	0.141	0.140	14.01
8	600	100	1 176	1 372	0.153	0.144	14.80
9	500	100	980	1 176	0.173	0.147	15.91
10	400	100	784	980	0.203	0.158	17.80
11	300	100	588	784	0.248	0.124	17.71
12	200	100	392	588	0.316	0.151	21.73
13	100	100	v196	392	0.398	0.110	20.58
14	600	200	2 352	1 372	0.064	0.219	12.14
15	500	200	1 960	1 176	0.068	0.222	12.60
16	400	200	1 568	980	0.101	0.237	15.31
17	300	200	1 176	784	0.102	0.236	15.56
18	200	200	784	588	0.159	0.260	20.26
19	100	200	392	392	0.306	0.242	27.42
“－”： No data.