Elsevier

Knowledge-Based Systems

Volume 85, September 2015, Pages 62-70
Knowledge-Based Systems

A cooperative belief rule based decision support system for lymph node metastasis diagnosis in gastric cancer

https://doi.org/10.1016/j.knosys.2015.04.019Get rights and content

Abstract

Lymph Node Metastasis (LNM) has become one of the most important prognostic factors regarding long-term survival in gastric cancer. As it is difficult for doctors to integrate multiple factors for a comprehensive analysis, Clinical Decision Support System (CDSS) is used to help the analysis. In this paper, a new Cooperative Belief Rule Based (CBRB) prototype CDSS is proposed. CBRB consists of two independent Belief Rule Base (BRB) systems and the final output is combined by the Evidential Reasoning (ER) approach. A corresponding new Cooperative CoEvolutionary Algorithm (CCEA) is proposed to train the proposed CBRB model that is nonlinear. A case study demonstrates that the proposed CDSS prototype can obtain the better performance than other CDSS.

Introduction

Gastric cancer has become one of the leading causes for cancer-related death around the world [1]. Lymph Node Metastasis (LNM) is one of most important prognostic factors regarding long-term survival [2], [3], [4], [5]. As such, diagnosing LNM accurately is very important. Currently, doctors diagnose LNM mainly according to the size of lymph node. However, large lymph nodes may be caused by inflammation, while small ones may be metastatic [6]. So a single lymph node size is not a strong predictor and more factors should be considered by applying Clinical Decision Support System (CDSS).

In previous research, several CDSSs have been proposed for LNM diagnosis, such as Artificial Neural Network (ANN) based CDSS [7], and Support Vector Machine (SVM) based CDSS [8]. However, both of them have some limitations. First of all, since they are black-box modeling methods, the reasoning process cannot be seen and doctors do not know which factors are more important for diagnosis. Moreover, as doctors play a critical role in diagnosis, it is important to diagnose LNM by using both clinical data and doctors’ knowledge [9].

According to the above analysis, a knowledge-based CDSS which can capture human judgments is more suitable for LNM diagnosis. In [9], a Bi-level Belief Rule Based (BBRB) CDSS was proposed by the authors. That CDSS is constructed based on a recently developed belief Rule-based Inference Methodology using the Evidential Reasoning approach (RIMER) [10]. The CDSS consists of two parts: (1) a Clinical domain knowledge base modeled by Belief Rule Base (BRB) and (2) a reasoning process supported by the Evidential Reasoning (ER) approach [11], [12], [13], [14], [15]. Compared to other knowledge based CDSSs, BBRB have some advantages as described in [9].

In BBRB, however, only the number and size of lymph nodes are utilized for LNM diagnosis. In fact, LNM is not only related with lymph node factors, but also with tumor factors [16], [17], [18], [19], [20]. To fully utilize the above factors, a Cooperative Belief Rule Based (CBRB) prototype CDSS is proposed in this paper. CBRB consists of two independent BRBs. One is used for modeling lymph node factors, while the other is used for modeling tumor factors. The final result is obtained by integrating the output of two BRBs, which is implemented by the ER approach. Meanwhile, as manually constructed belief rule may not be accurate, it is necessary to train CBRB. In this paper, a corresponding new Cooperative CoEvolutionary Algorithm (CCEA) is designed, which can be used to optimize the two BRBs and weight coefficients simultaneously.

The rest of the paper is organized as follows. The problem formulation is shown in Section 2. In Section 3, the CBRB CDSS prototype is presented. A new CCEA based method for optimizing CBRB is developed in Section 4. In Section 5, the proposed CDSS prototype for diagnosing LNM is presented. The validation of BBRB is discussed in Section 6. This paper is concluded in Section 7.

Section snippets

Problem formulation

Suppose that T=[T1,T2,,TM] is the set of diagnostic factors which are extracted from tumor, while L=[L1,L2,,LN] is the set of factors from lymph nodes, where M and N are the number of attributes for the two type of factors respectively. Suppose that PT and PL are the corresponding parameter vectors for the two BRBs, ω=[ω1,ω2] is the set of weight coefficients that represent the relative importance for each BRB. In other words, the problem is in essence to construct a causal relationship

CBRB prototype CDSS

As CBRB is constructed on the basis of BRB, BRB will be briefly described at first. Then the proposed CBRB model will be presented.

New optimization model and CCEA for training CBRB

In this section, a new optimization model for training CBRB and a corresponding CCEA based optimization algorithm is proposed.

CBRB prototype CDSS for diagnosing LNM

In this section, the proposed CBRB CDSS prototype is utilized for LNM diagnosis. It consists of two parts: (1) constructing each BRB model in CBRB system and (2) the training process for optimizing CBRB.

An experimental case study

In this section, CBRB is validated using a set of real patient data. Just as in [9], the 2-cross-validation approach is used. To better analyze the performance, Confusion Matrix (CM) is utilized to show the results. In this matrix, each column represents the instances in a predicted stage, and each row represents the instances in an actual stage. In CM, two evaluated indexes are used, that is: (1) User Accuracy (UA); (2) Procedure Accuracy (PA). UA represents the ratio of the number of

Conclusions

In this paper, a Cooperative Belief Rule Based (CBRB) CDSS prototype was proposed for LNM diagnosis in gastric cancer. CBRB consists of two independent BRBs and the final output is obtained by using the ER approach. In addition, a corresponding CCEA based method was proposed for training CBRB. By utilizing both the tumor and lymph node features, CBRB can obtain better diagnostic performance. A comparative case study on current CDSSs showed that CBRB performed better than other methods, needless

Acknowledgments

The authors would like to thank their collaborators of Beijing Cancer Hospital for their suggestions and impressive work and thank Professor Dong-Ling Xu from Manchester Business School, The University of Manchester for her suggestive comments. This research was supported in part the National Basic Research Program (973 Program) of China (No. 2013CB329402), in part by the National Natural Science Foundation of China (Nos. 61173090, 61173092, 61303119, 61271302, 61272282), in part by the

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