A simple blood test may enable doctors to rule out cancer in patients presenting with certain symptoms, saving time and even sparing patients the need to undergo invasive procedures such as colonoscopies and biopsies. Alternatively, it could be a useful aid for investigating patients who are suspected of having a cancer that is currently hard to diagnose.
The test, called the Lymphocyte Genome Sensitivity (LGS) assay, measures the damage caused to the DNA of white blood cells that have been subjected to different intensities of ultraviolet light (UVA). According to its developers, the test serves as a kind of yardstick. By determining the degree of DNA damage, the test distinguishes between white blood cells that come from patients with cancer, patients with precancerous conditions, and healthy patients.
The LGS assay, which was devised by researchers at the University of Bradford, is a modified comet assay. Here, UVA damage is observed in the form of pieces of DNA that respond to an electric field by forming a comet-like tail—the longer the tail, the greater the DNA damage.
Details of the LGS assay appeared July 25 in FASEB Journal, in an article entitled, “Sensitivity and specificity of the empirical lymphocyte genome sensitivity (LGS) assay: Implications for improving cancer diagnostics.” The article described how the researchers looked at blood samples taken from 208 individuals. Ninety-four healthy individuals were recruited from staff and students at the University of Bradford, and 114 blood samples were collected from patients referred to specialist clinics within Bradford Royal Infirmary prior to diagnosis and treatment. The samples were coded, anonymized, randomized, and then exposed to UVA light through five different depths of agar.
The study was led by Diana Anderson, Ph.D., a professor from the University of Bradford’s School of Life Sciences. “We know that white blood cells are under stress when they are fighting cancer or other diseases, so I wondered whether anything measurable could be seen if we put them under further stress with UVA light,” explained Dr. Anderson. “We found that people with cancer have DNA that is more easily damaged by ultraviolet light than other people, so the test shows the sensitivity to damage of all the DNA—the genome—in a cell.”
In the study, measurements derived from the Olive tail moment—the product of the tail length and the fraction of total DNA in the tail—were correlated with patients who were ultimately diagnosed with cancer (58), patients with precancerous conditions (56), and healthy patients (94). Early results have shown the method gives a high degree of accuracy diagnosing cancer and precancerous conditions from the blood of patients with melanoma, colon cancer, and lung cancer.
“These are early results completed on three different types of cancer, and we accept that more research needs to be done; but these results so far are remarkable,” noted Dr. Anderson. "Whilst the numbers of people we tested are, in epidemiological terms, quite small, in molecular epidemiological terms, the results are powerful. We’ve identified significant differences between the healthy volunteers, suspected cancer patients, and confirmed cancer patients of mixed ages at a statistically significant level of P < .001.”
The authors of the FASEB Journal article concluded that the modified comet assay could represent a standalone test or serve as an adjunct to other investigative procedures for detecting cancer. To further evaluate the usefulness of LGS assay as a cancer diagnostic test, investigators at the Bradford Royal Infirmary are conducting a trial. The investigators hope to establish the effectiveness of the LGS test in correctly predicting which patients referred by their GPs with suspected colorectal cancer would, or would not, benefit from a colonoscopy—currently the preferred investigation method.