Biomarkers present in cells shed into urine may be useful tools for predicting and detecting bladder cancer, according to the results of a study recently published in the Journal of the National Cancer Institute.
Bladder cancer is a common cancer worldwide, with approximately 260,000 new cases and 115,000 deaths each year. Unfortunately, most bladder cancers are not diagnosed until the cancer has reached advanced stages and is more difficult to treat. There are currently no effective screening procedures for detecting bladder cancer early before symptoms are present. Approximately 25% of all bladder cancer cases are related to occupational exposure to chemicals such as benzidine. Because workers exposed to some chemicals are at an increased risk of developing bladder cancer, researchers continue to explore potential screening methods that would allow for earlier detection of this cancer.
Researchers from the University of Oklahoma conducted a study in the People’s Republic of China to examine three biomarkers of bladder cancer. The study involved 1,788 men exposed to benzidine at work and 373 non-exposed men who were followed from 1991 through 1997. The workers provided urine samples initially and after three years. The researchers then examined cells from these urine samples for the presence of three biomarkers: DNA ploidy, p300 (a bladder tumor antigen), and G-actin (a cytoskeletal protein). The workers were then divided into low, moderate and high-risk groups based on their biomarker profiles.
During the study, 28 exposed and 2 non-exposed workers were diagnosed with bladder cancer. Most of the bladder cancer cases occurred in the high-risk group. The positive biomarker profile proved to be an effective predictive method. On average, individuals in the high-risk group were predicted to have bladder cancer 15 months prior to clinical detection of their tumors and individuals in the moderate-risk group were predicted to have cancer 33 months prior to detection. The researchers found that workers who tested positive for either the DNA ploidy or the p300 were 20 times more likely to develop bladder cancer than workers who tested negative for these biomarkers. Furthermore, workers who tested positive for both DNA ploidy and p300 were 80 times more likely to develop bladder cancer than those who tested negative. They found that G-actin was a poor biomarker for risk assessment.
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The researchers concluded that exposed workers at risk for bladder cancer can be individually stratified, screened, monitored and diagnosed based on biomarker profiles. Because the average time between initial carcinogen exposure and the subsequent development of bladder cancer is 18 years, biomarker profiles could ultimately play an important role in prevention, as there is an ample window of time to detect premalignant conditions. (Journal of the National Cancer Institute, Vol 93, No. 6, pp. 427-436, 2001)