AIM: To determine the utility of the Asia-Pacific colorectal screening (APCS) scoring system and metabolic syndrome components in individual screening for sporadic colorectal cancer.

METHODS: The subjects were patients admitted to the Peking University People’s Hospital for colonoscopy between October 2012 and July 2013. Clinical information, including patient willingness to undergo colonoscopy, medical history, endoscopic findings, histology, and other information, was collected, and the patients were grouped according to APCS scores and the presence of metabolic syndrome components. Colorectal tumor detection rates were compared between the groups.

RESULTS: A total of 219 patients were included in the study, 108 were male and 111 were female, resulting in a male-to-female ratio of 1:1.03. The average age of the patients was 56.8 ± 13.7 years. According to APCS scores, 88 (40.2%) patients were included in the average-risk (AR) group, 113 (51.6%) patients were included in the moderate-risk (MR) group, and 18 (8.2%) patients were included in the high-risk (HR) group. Colorectal tumors were detected in 69 (31.5%) subjects, and the detection rates in the AR, MR, and HR groups were 15.9%, 36.3%, and 77.8%, respectively. The difference in the detection rates between the three groups was statistically significant (P < 0.01). The combined detection rate of colorectal tumors in the APCS MR and HR groups was 42.0%. However, patients in the MR and HR groups who presented with metabolic syndrome components, in particular obesity, exhibited a significantly higher colorectal tumor detection rate (59.5%) than did those without these components (19.2%, P < 0.01) and those who underwent colonoscopy because of doctor’s recommendation (36.5%, P < 0.01).

CONCLUSION: The APCS scoring system can be used in individual screening for sporadic colorectal cancer. The combined use of APCS scores and the metabolic syndrome components, in particular obesity, will significantly improve the efficacy of individual colorectal cancer screening.

Colorectal cancer (CRC) is one of the most common malignant tumors worldwide[1-3]. Both the incidence and associated mortality rates of CRC in China have increased because of improved standards of living and changes in eating habits[4]. In most cases, CRC is sporadic and develops from adenomas. As effective CRC prevention methods are lacking, the best method to prevent the morbidity associated with CRC is to improve the detection rate of early-stage disease. A growing body of evidence has shown that detection and elimination of lesions at the precursor or early stage can reduce both the incidence of and mortality from CRC[5]. The decreased incidence of CRC in the United States over the past 2 decades has been attributed by some efficient CRC screening[6].

Many studies have recommended screening programs for CRC[7-9]. Among them, the Asia-Pacific colorectal screening[2] (APCS) system, reported in 2011, uses age, gender, a family history of colorectal tumors, and smoking history as the factors to calculate scores. Individuals are categorized into 3 groups according to these scores: the average-risk (AR), moderate-risk (MR), and high-risk (HR) groups. Colonoscopy is recommended for individuals in the HR group. The APCS scoring system is simple and convenient for outpatient screening; however, it was proposed only recently, and therefore, its effectiveness requires further evaluation. Because the APCS system was established using asymptomatic individuals, whether it is useful for individual screening in symptomatic outpatients was discussed in this study.

Metabolic syndrome (MS) comprises the metabolic risk factors of cardiovascular disease and type 2 diabetes, which mainly include obesity, dyslipidemia, hypertension, hyperglycemia, and insulin resistance[10]. Because of the adoption of Western dietary habits and life-style, many Asian countries have witnessed a substantial increase in the prevalence of obesity and MS over the past few decades[11,12].

A large number of epidemiological studies have shown that MS components are closely related to the occurrence of colorectal tumors[13-17]. However, the APCS scoring system does not incorporate MS components. Therefore, in this study, we assessed the utility of the APCS system and the presence of MS components in outpatient screening for CRC by stratifying individuals according to these parameters.

Researchers at the National University of Singapore conducted a study on tertiary hospitals in 11 Asian cities, including 2752 asymptomatic individuals who underwent screening colonoscopy. The researchers developed the APCS scoring system based on the results of multivariate logistic regression analysis of the risk factors for colorectal tumors[9]. In the validation group, the rates of advanced neoplasia in the AR, MR, and HR groups were 1.3%, 3.2%, and 5.2%, respectively. Patients in the MR and HR groups had a 2.6-fold (95%CI: 1.1-6.0) and 4.3-fold (95%CI: 1.8-10.3) higher rate of advanced neoplasia, respectively, than patients in the AR group. In our study, we observed colorectal tumor detection rates of 15.9%, 36.3%, and 77.8%, respectively, for the AR, MR, and HR groups, and the detection rates for advanced colorectal tumor were 2.3%, 9.7%, and 27.8% in these groups, respectively. The differences in the detection rates between the 3 groups were statistically significant, suggesting that APCS scoring system was useful in colorectal tumor screening for symptomatic outpatients, although the APCS scoring system was established using asymptomatic individuals. In addition, the APCS scoring system is simple and convenient for clinical use. In this study, the colorectal tumor detection rate was significantly higher than that in the APCS study; a possible reason for this difference is that many patients who visited the clinic had related symptoms and risk factors such as a history of colorectal polyps or CRC. Patients with a history of colorectal polyps might have recurrence rates exceeding 55.7%[15], and therefore, the colorectal tumor detection rate is higher in those patients than in the general population.

Numerous studies have indicated that MS components and related diseases are significantly associated with the development of colorectal tumors, and MS is a significantly independent element that influences the survival of the CRC[14-18]. Obesity is a key component of MS[19], and systematic reviews[20,21] revealed that obesity is a statistically significant risk factor for CRC. Therefore, we further stratified patients in the MR and HR groups according to these risk factors. When patients in the MR/HR group were stratified according to the presence of obesity, the colorectal tumor detection rate significantly increased (59.5% vs 19.2% for the MR/HR group without obesity, P < 0.01). Thus, MS components, especially obesity, are closely related to the onset of colorectal tumors.

Our previous studies[15,16] demonstrated that an increase in the number of MS components is related to an increased proportion of advanced colorectal tumors among all colorectal tumors. The number of MS components is also related to tumor recurrence. Patients with colorectal tumors that are not associated with any MS components have a recurrence rate of 18.42% within 1-3 years after initial treatment, whereas those with 1, 2, or ≥ 3 components have recurrence rates of 59.52%, 75%, and 77.78%, respectively. This finding suggests that the number of MS components is positively correlated with the risk of colorectal tumor development. This study revealed that the colorectal tumor detection rate increased as the number of MS components increased; however, this increase did not reach statistical significance, which was probably due to the small sample size.

Individual screening, also known as opportunistic screening, comprises clinical screening and a face-to-face examination. This may be performed when patients request screening from doctors or doctors prescribe screening tests on the basis of the presence of risk factors. In fact, most early CRC diagnoses in China result from individual screening recommended by doctors in hospital[22]; however, neither doctors nor patients have clear guidelines to follow. In China, the CRC screening program involves screening methods such as the sequential fecal occult blood initial screening method[23]. Even with immunoassays of fecal occult blood, the detection rate of early-stage CRC is relatively low[23,24]. Thus, in CRC screening programs, a survey of high-risk factors for CRC should be emphasized, so that patients in the high-risk group can undergo screening colonoscopy without delay.

According to former studies, the extent of knowledge regarding CRC that primary care doctors and the general population have greatly influences compliance with CRC screening[25,26]. Given the limited medical resources, we should identify high-risk patients for prior colonoscopy screening. In the clinic, doctors’ decisions are greatly influenced by personal experiences. Most doctors are not familiar with specific CRC screening principles, and many patients fear colonoscopy. This study illustrated that the combined use of the APCS score and the presence of MS components such as obesity had a significantly better effect on CRC screening than did physician advice or the patient’s willingness to undergo colonoscopy. We suggest that the effects of the APCS scores as well as those of MS components on CRC onset be advocated in doctors and among the general population. Increased compliance with CRC screening should be ensured among patients in the APCS MR/HR group, especially among those with MS components, particularly obesity, to increase the efficiency of individual CRC screening programs and promote the accumulation of experiences and data that will provide evidence for improving CRC screening in China.