Serum bilirubin and risk of colorectal cancer

Serum Total Bilirubin and Risk of Cancer: A Swedish Cohort Study and Meta-Analysis

Simple Summary

Several studies published to date have shown inconclusive results in the association between serum bilirubin and risk of site-specific cancer types and overall cancer. Therefore, there is a need to further investigate this association. Data from the large Swedish Apolipoprotein Mortality Risk (AMORIS) cohort study was used. We found that overall high levels of bilirubin had no association with overall cancer risk. However, a positive association was found between melanoma and breast cancer risk. On the other hand, an inverse association was found between high levels of bilirubin and risk of gynecological and lung cancers. Further studies are required to establish if bilirubin can be used as a biomarker for risk assessment and/or as a novel therapeutic target.

Abstract

Bilirubin has strong antioxidant properties that have been hypothesized to be preventive against the development of cancer. Thus, we aimed to investigate the association between serum total bilirubin (STB) and risk of overall and site-specific cancers in the large Swedish Apolipoprotein Mortality Risk (AMORIS) cohort. We also performed a systematic review and meta-analysis for specific cancer types (colorectal, breast and lung). We found no association between high levels of STB and risk of overall cancer. Regarding site-specific cancer, there was an inverse association between increased STB and lung cancer (Hazard Ratio (HR) for the 4th quartile (Q4) vs. Q1: 0.50; 95%CI: 0.44–0.59) and gynecological cancer (HR for Q4 vs. Q1: 0.86; 95%CI: 0.76–0.99). A positive association was found with melanoma (HR for Q4 vs. Q1: 1.25; 95%CI: 1.06–1.47) and breast cancer (HR for Q4 vs. Q1: 1.13; 95%CI: 1.01–1.25) risk. The meta-analysis showed an inverse association between high levels of STB and risk of lung cancer (Relative risk (RR): 0.69; 95%CI: 0.55–0.86). No associations were seen for colorectal and breast cancer risk. Further studies are required to establish if bilirubin can be used as a biomarker for risk assessment and/or as a novel therapeutic target.

The prognostic impact of serum bilirubin in stage IV colorectal cancer patients

BACKGROUND

Bilirubin played a great role in antioxidation and anticancer and has been considered as a promising prognostic factor of non-liver disease-related death in various cancers. The aim of this study was to assess the prognostic value of pre-treatment serum bilirubin in stage IV CRC patients.

METHODS

Serum bilirubin including TBIL, DBIL, and IBI which were tested at pre-treatment were investigated in 154 stage IV CRC patients in Zhongda Hospital, Nanjing, China, from July 2005 to July 2011. X-tile program was used to determine the optimal cut-off values of these three biomarkers. Kaplan-Meier analysis, univariate, and multivariate cox regression as well as time-dependent ROC curve analysis were performed to evaluate the relations between serum bilirubin and survival outcomes.

RESULTS

We got the results that the optimal cut-off points of serum TBIL, DBIL, and IBI levels were 12.9, 6.1, and 4.8 μmol/L, respectively. Univariate analysis showed that elevated TBIL, DBIL, and CEA were significantly associated with poor 5-year OS in stage IV CRC patients. Multivariate cox analysis indicated that the high DBIL (HR=1.603, 95%CI=1.053-2.442, P<.028) and CEA (HR=1.785, 95%CI=1.123-2.837, P=.014) could be identified as independent factors for poor OS. Furthermore, time-dependent ROC curves demonstrated that high DBIL had similar prognostic efficacy as elevated CEA for poor OS (AUC=0.63 and 0.61, respectively).

CONCLUSIONS

Pre-treatment elevated TBIL and DBIL levels were associated with poor OS in stage IV CRC patients. Moreover, DBIL could be considered as an independent prognostic biomarker for OS. Furthermore, DBIL had similar prognostic efficacy as CEA for OS.

Physiological antioxidative network of the bilirubin system in aging and age-related diseases

Oxidative stress is detrimental to life process and is particularly responsible for aging and age-related diseases. Thus, most organisms are well equipped with a spectrum of biological defense mechanisms against oxidative stress. The major efficient antioxidative mechanism is the glutathione system, operating a redox cycling mechanism for glutathione utilization, which consists of glutathione and its peroxidase and reductase. However, this system is mainly effective for hydrophilic oxidants, while lipophilic oxidants require another scavenging system. Since many age-related pathological conditions are related to lipid peroxidation, especially in association with the aging process, the physiological role of the scavenging system for lipophilic oxidants should be considered. In this regard, the biliverdin to bilirubin conversion pathway, via biliverdin reductase (BVR), is suggested to be another major protective mechanism that scavenges lipophilic oxidants because of the lipophilic nature of bilirubin. The efficiency of this bilirubin system might be potentiated by operation of the intertwined bicyclic systems of the suggested redox metabolic cycle of biliverdin and bilirubin and the interactive control cycle of BVR and heme oxygenase. In order to combat oxidative stress, both antioxidative systems against hydrophilic and lipophilic oxidants are required to work cooperatively. In this regard, the roles of the bilirubin system in aging and age-related diseases are reassessed in this review, and their interacting networks are evaluated.