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ORIGINAL ARTICLE
Year : 2015  |  Volume : 11  |  Issue : 6  |  Page : 168-172

Lower serum levels of bilirubin in the newly diagnosed lung cancer patients: A case-control study in China


1 Department of Clinical Laboratory, Zhejiang Cancer Hospital, Zhejiang Key Laboratory of Radiation Oncology, Beijing 100049, China
2 Department of Clinical Laboratory, Aerospace Central Hospital, Haidian, Beijing 100049, China
3 Department of Clinical Laboratory, Zhejiang Cancer Hospital, Hangzhou 310022, Zhejiang, Beijing 100049, China

Date of Web Publication26-Oct-2015

Correspondence Address:
Wen-Hu Chen
Zhejiang Key Laboratory of Diagnosis and Treatment Technology Research on Chest Tumor (Lung, Esophagus), 38 Guangji Road, Hangzhou 310022, Zhejiang
China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-1482.168179

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 > Abstract 

Purpose: A few prospective studies demonstrated that bilirubin levels were inversely associated with the risk of lung cancer. However, the retrospective study about the relationship between bilirubin levels and lung cancer in China was not available. So, we want to know whether there has a difference in serum bilirubin concentrations between normal people and lung cancer patients.
Materials and Methods: Using a case-control study, we investigated the bilirubin levels in 317 patients with lung cancer and 317 age-, sex-matched controls from Zhejiang Cancer Hospital. Furthermore, we analyzed the associations between serum bilirubin expressions and baseline clinical features of lung cancer patients using a Wilcoxon rank sum test.
Results: Bilirubin levels, including total bilirubin, direct bilirubin, and indirect bilirubin, were significantly lower in human lung cancer serum relative to normal control (P < 0.001), and the older (>50 years) had higher bilirubin levels compared with the younger (27–50 years) in lung cancer group. Besides, the duration of smoking was negatively related to bilirubin levels, but they did not reach statistical significance except for indirect bilirubin (P = 0.041). However, there was no difference in bilirubin levels between small cell lung cancer (SCLC) and non-SCLC (NSCLC), and we did not find that the bilirubin levels were correlated with sex, drinking status in patients of lung cancer.
Conclusion: Serum total bilirubin, indirect bilirubin, and direct bilirubin levels of the patients with lung cancer were all significantly lower than those of control group (P < 0.001). Lower levels of bilirubin may be a risk factor for lung cancer, and it could serve as a potential screening biomarker for lung cancer. Large-scale investigations and additional improvements are urgently needed to demonstrate the mechanism and molecular pathway in order to achieve the clinical utility in the future.

Keywords: Bilirubin, biomarker, lung cancer, serum


How to cite this article:
Song Q, Wang B, Wang S, Zhang YM, Chen WH. Lower serum levels of bilirubin in the newly diagnosed lung cancer patients: A case-control study in China. J Can Res Ther 2015;11, Suppl S2:168-72

How to cite this URL:
Song Q, Wang B, Wang S, Zhang YM, Chen WH. Lower serum levels of bilirubin in the newly diagnosed lung cancer patients: A case-control study in China. J Can Res Ther [serial online] 2015 [cited 2019 Dec 7];11:168-72. Available from: http://www.cancerjournal.net/text.asp?2015/11/6/168/168179


 > Introduction Top


Cancer is the leading cause of death in economically developed countries and the second leading cause of death in developing countries. On the basis of global cancer statistics, 10.9 million new cancers are diagnosed every year, of which 1.35 million are lung cancer cases. About 6.7 million patients die from cancer each year, and lung cancers are responsible for 1.18 million deaths, yearly.[1] In 2013, lung cancer was one of the most common reasons for cancer-related mortality in the world.[2] The statistics results showed the cancer incident cases were 3.09 million and 1.96 million cancer deaths with the incidence rate of 235.23/100,000 and mortality of 148.81/100,000 in China. While lung cancer becomes the most common cancer and the leading cancer death both in urban and rural areas, with an incidence rate of 92.06/100,000, and with mortality of 88.41/100,000.[3]

When lung cancer is diagnosed with localized disease, the 5-year survival rate is 53%. However, the survival rate decreases to about 24% for regional tumors, and to <5% while it is distant.[4] A few large population studies have showed that relatively lower survival was associated with delays in diagnosis.[5],[6] Low-dose spiral computed tomography (LDCT) scanning was used to detect lung cancer as one of the most common methods in smokers who had a history of smoking 30 packs of cigarettes each year at the ages of 55 to 74 years old.[7],[8] Nevertheless, there was a rising lung cancer risk because of LDCT scanning with radiation.[9] Therefore, it is urgent to identify the noninvasive and cheaper biomarkers for accurate and reliable diagnosis.

Serum bilirubin is the ultimate breakdown product of heme catabolism in the body and increased bilirubin contributes to identify hepatobiliary and hemolytic diseases.[10],[11] It is important in relationship to several processes involved in drug metabolism.[12] The levels of serum bilirubin are higher in men than women and decreases with age.[13],[14],[15] Other determinants of serum bilirubin levels include smoking status,[13],[16],[17],[18],[19],[20] fasting status.[14]

In both retrospective and prospective studies, we found evaluated serum bilirubin was associated with decreased risks for plenty of diseases, such as cardiovascular disease,[16],[21] pulmonary disease,[22] diabetes,[23] rheumatoid arthritis,[24] incidence of colon cancer,[25] lung cancer risk and mortality,[17],[22],[26] all-cause and cancer mortality.[27] However, the association between bilirubin levels and lung cancer have not been fully understood because of absent reports in retrospective studies. No information such as histological grades and stages of lung cancer is available. Although, a few researches have proved that serum bilirubin is significant lower in lung cancer than normal control group, there is no Chinese data, so we do not know whether the conclusion is suitable for China, and it is also lack of retrospective study to support it, what's more, no information such as histological grades and stages of lung cancer is available.

Considering all these factors, we conducted to analyze whether the serum bilirubin concentrations in the lung cancer patients who were newly diagnosed were different from age- and sex-matched healthy controls in Southeast China. Besides, we aimed to investigate the links between bilirubin levels and clinicopathological features, such as histological grades and stages of lung cancer.


 > Materials and Methods Top


Subjects

A total of 340 lung cancer specimens obtained from Chinese patients who were newly diagnosed and treated from June 2010 to July 2014 in Zhejiang Cancer Hospital (Hangzhou, China) were available for examination in this analysis. Clinical tumor stage was done by computed tomography scans of the chest and upper abdomen, a magnetic resonance imaging scan of the brain, and nuclear bone scan, confirmed by pathological examination. For the stage of lung cancer, the tumor node metastasis stage (developed by the American Joint Committee on Cancer) was used. Exclusion criteria included a history of liver or gall bladder disease, uncertain smoking cessation, or abnormal liver function. 16 of the 340 patients who were initially recruited to the study had abnormal liver function tests, two had uncertain smoking cessation, and five had liver or gall bladder disease in the past. As a result, 317 individuals met the inclusion criteria and only serum from these participants, and their respective controls were measured for bilirubin.

For each case of lung cancer, control was selected at random from subjects who underwent healthy examinations, matched on age (mean 61, range: 27–81 years), and sex. None of them had previously been diagnosed with a malignancy. The study was conducted with the consent of the ethics committee of Zhejiang Cancer Hospital in China. The informed consent requirement was obtained from all participants and controls.

Measurements

Blood samples were obtained from peripheral venous after 12 h of fasting. They were centrifuged at 3000 rpm for 5 min at 4°C to completely remove cellular components, and the supernatant (serum) was collected. Serum levels of total bilirubin and direct bilirubin were measured on the Hitachi-7600 automated chemistry analyzer (Hitachi Ltd., Tokyo, Japan). Indirect (uncongulated) bilirubin was calculated as (total − direct bilirubin). All analyses were performed by the clinical laboratory in Zhejiang Cancer Hospital.

Cigarette smoking status was classified into two groups: "Current nonsmokers" (never-smokers and ex-smokers who have quit smoking more than half a year) and "current smokers." Alcohol consumption was divided into two groups based on drinking habits. We classified alcohol consumption as nondrinker and drinker (any amount of alcohol).

Statistical analysis

All analyses were conducted using the software SPSS 16.0 software (SPSS, Inc., Chicago, IL, USA). Normality of distribution of variables was tested by Kolmogorov–Smirnov tests. Baseline characteristics and bilirubin values were assessed using means (standard deviation) for continuous variables and frequency (proportion) for categorical variables. The comparison of bilirubin metabolites between cases and controls were estimated by the Wilcoxon rank sum test. Subjects were compared for differences in bilirubin data using a Wilcoxon rank sum test according to patient characteristics, including gender, age, smoking status, alcohol consumption, histology subtype, and stage. A value of P < 0.05 (two-tailed) was considered to be statistically significant.


 > Results Top


The normal controls

There were 317 persons in the normal control (275 men, 42 women), the serum bilirubin levels, and the baseline characteristics are listed in [Table 1]. Serum total bilirubin, indirect bilirubin, and direct bilirubin concentrations of healthy controls in men were all significantly higher than in women (P < 0.001). The median mean serum total bilirubin levels were 14.6 μmol/L (range: 8.8–20.4 μmol/L) in men, and 10.3 μmol/L (range: 6.6–14.0 μmol/L) in women. The bilirubin levels in the older (>50 years) were higher, but they did not reach statistical significance except for indirect bilirubin (P = 0.048).
Table 1: Association between serum bilirubin levels and various characteristics in healthy controls

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Decreased bilirubin concentrations in lung cancer patients

Serum total bilirubin, indirect bilirubin, and direct bilirubin levels of the patients with lung cancer were all significantly lower than those of control group (P < 0.001) [Figure 1]. It revealed that the levels of serum bilirubin were a potential marker for discriminating lung cancer patients from healthy controls.
Figure 1: Boxplot of serum bilirubin levels in normal controls and patients with lung cancer. TBIL = Total bilirubin, IBIL = Indirect bilirubin, DBIL = Direct bilirubin

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Bilirubin levels with clinical characteristics in lung cancer patients

There were 317 patients in lung cancer group (275 men, 42 women), the serum bilirubin levels, and the baseline characteristics are listed in [Table 2]. It is obvious that there were positive relationships of total bilirubin, indirect bilirubin, and direct bilirubin concentrations with age in lung cancer patients. Direct bilirubin levels in patients with early stage were lower than that in advanced stage (P = 0.039), and total bilirubin and indirect bilirubin also showed the same trend, but they did not reached the statistical significance. While current smoking status was negatively associated with indirect bilirubin. The results showed that bilirubin levels had nothing to do with sex, drinking status, and histological subtype in patients with lung cancer [all P > 0.05, [Table 2].
Table 2: Association between serum bilirubin levels and various characteristics in patients of lung cancer

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The association between bilirubin levels and smoking status

Subjects with high indirect bilirubin levels were current nonsmokers (P = 0.041). The mean concentration was 7.0 μmol/L (range: 2.8–11.2 μmol/L) in current nonsmokers, and 6.0 μmol/L (range: 3.2–8.8 μmol/L) in current smokers. Total bilirubin and direct bilirubin showed the same trend but did not reach statistical significance (P = 0.138, P = 0.736). The mean total bilirubin and direct bilirubin levels were higher (10.3 μmol/L and 3.4 μmol/L) in current nonsmokers compare with those (9.2 μmol/L and 3.3 μmol/L) in current smokers [Figure 2].
Figure 2: The relationship between serum bilirubin levels and smoking status in lung cancer patients. TBIL = Total bilirubin, IBIL = Indirect bilirubin, and DBIL = Direct bilirubin

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 > Discussion Top


A few prospective studies about the relationship between bilirubin and lung cancer suggested a protective effect of bilirubin against lung cancer. One UK population-based cohort study showed a negative relation between bilirubin and lung cancer.[22] Another severance cohort study which used Korea primary care data found the consistent result.[26] To our best knowledge, the present study is the first retrospective analysis to investigate the relationship between bilirubin levels and baseline characteristics of newly diagnosed lung cancer patients in China. Furthermore, our study is also the first using a sex-, age-matched normal group to assess the difference in serum bilirubin levels, so we can effectively avoid the test errors due to the random selection.

We observed the serum bilirubin concentrations were higher in men than in women of healthy controls, which is in agreement with early studies.[22],[26] However, there were no difference in bilirubin levels between men and women of lung cancer patients. This was inconsistent with previous reports, maybe due to the different ratio of gender in the included subjects.[14],[15] In our study, the proportion of women was lower than those in previous studies. Even though bilirubin levels were similar in men and women of cases, there was significantly lower in cases than in controls.

Previous studies showed bilirubin levels decreased with age while in this analysis indirect bilirubin levels in the older (>50 years) was higher compared with, the younger (27–50 years) of healthy controls.[13] Serum total bilirubin, indirect bilirubin, and direct bilirubin concentrations of healthy controls in men were all significantly higher than in women (P < 0.001). The inconsistent results could owe to different regions. Another reason was the subjects were only divided into two groups according to age: The older (>50 years) and the younger (27–50 years). The younger group needs to be subdivided even further.

We found advanced stage was positively associated with direct bilirubin concentrations. Most with advanced lung cancer had hepatic metastasis, which attributed to the high bilirubin levels. There were no association between bilirubin levels and histological grades and drinking status. As we did not adjusting for potential confounders, such as smoking status, gender, and age, it was not very suitable to summarize what we had concluded.

One epidemiological study among the Belgian population showed total serum bilirubin was lower in current smokers than never-smokers and ex-smokers.[28] Besides, there was another study showed smoking cessation is followed by increases in indirect bilirubin levels reached 0.06 mg/dl.[17] So we divided smoking status into two groups: Current smokers, never-smokers and ex-smokers (who quit smoking more than 6 months). In this study, the indirect bilirubin mean was lower in current smokers compared with never-smokers and ex-smokers.

This study has a few limitations: Frist of all, there were no difference in bilirubin levels between men and women with lung cancer. Besides, due to the low number of lung cancer in women, the analysis was not grouped by sex. Second, we were not able to take some potential confounders into account, such as fasting status, body mass index (BMI) index. Because the fasting status was not listed in the questionnaire, we could not have access to this information. While the Chinese BMI index difference was not very wide, BMI index was not included in the baseline characteristics of lung cancer patients.


 > Conclusion Top


Serum total bilirubin, indirect bilirubin, and direct bilirubin levels of the patients with lung cancer were all significantly lower than those of control group. This was the first retrospective study showed the concentrations of serum bilirubin in men were similar with women and increased with age in China. Current smoking status was inversely associated with indirect bilirubin while the advanced stage was positively related to direct bilirubin. Besides, there was no association between bilirubin levels and histological grades and drinking status. Lower levels of bilirubin may be a risk factor for lung cancer, and it could serve as a potential screening biomarker for lung cancer. Our sample size was relative small, and the relationship of bilirubin levels with clinical characteristics of lung cancer patients should be explored by conducting further studies with larger sample numbers. Additionally, the mechanism and molecular pathway of bilirubin working as a protective factor against cancer is unknown. This is an area that clearly needs further research.

Acknowledgments

We thank all subjects who participated in this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
 > References Top

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    Figures

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    Tables

  [Table 1], [Table 2]



 

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