Washington: Elevated levels of bilirubin in the blood is said to indicate that something has gone wrong with the liver.
Now researchers at The University of Texas MD Anderson Cancer Center have found that male smokers with low levels of the yellow-tinged chemical are at higher risk for lung cancer and dying from the disease.
"Our study indicates male smokers with low levels of bilirubin are a high-risk group that can be targeted with smoking cessation help, low-dose spiral CT screening of their lungs and other preventive measures," said senior author Xifeng Wu, M.D., Ph.D., professor and chair of MD Anderson`s Department of Epidemiology and the Betty B. Marcus Chair in Cancer Prevention.
The researchers started with an objective analysis of levels of metabolites - substances produced during metabolism. Bilirubin is produced during the breakdown of old blood cells.
They analyzed 60 samples divided into three groups known as "trios" - normal controls, early stage and late stage non-small cell lung cancer patients. The top three metabolites were validated in two more groups of 50 and 123 trios.
Bilirubin makes sense as a protective agent because of its anti-oxidant, anti-inflammatory and anti-proliferative effects. "It`s plausible that bilirubin protects against lung cancer by scavenging free radicals and carcinogens associated with smoking," said study presenter Fanmao Zhang, a doctoral candidate in epidemiology.
Smokers in the two middle cohorts of bilirubin levels also had higher lung cancer risk than those in the highest quartile. As an objective risk index for lung cancer and all-cause mortality, low levels of bilirubin should send an urgent message to quit smoking, said Chi Pang Wen, M.D., Ph.D., co-lead author from National Health Research Institutes, Taiwan.
The next step, Wu said, is to evaluate the predictive value of serum bilirubin in heavy smokers and to establish a risk prediction model that incorporates bilirubin and other biomarkers with clinical and epidemiological data to improve the efficiency of lung cancer risk prediction.
The study was presented at the AACR Annual Meeting 2013 in Washington, D.C.