January 24, 2008, Boston, MA--A study appearing in the January 15 issue of Clinical Cancer Research demonstrates that SELDI-TOF mass spectrometry for proteomic profiling is more accurate than traditional biomarkers in distinguishing liver cancer patients from patients with hepatitis C liver cirrhosis, particularly with regard to identifying patients with small, curable tumors. Led by researchers at Beth Israel Deaconess Medical Center (BIDMC), the study could help lead to earlier diagnostic methods and subsequent treatments for liver cancer.
"Proteomics represents a potentially powerful tool for the serologic recognition of protein profiles associated with cancer," explains co-senior author Towia Libermann, PhD, Director of the Genomics Center at BIDMC and Associate Professor of Medicine at Harvard Medical School. "Although this particular proteomics technology, SELDI-TOF MS [surface enhanced laser desorption/ionization time of flight mass spectrometry] had already proven capable of identifying liver cancer in some limited studies, this was the first time that the technology was compared side-by-side with the clinical standard biomarker in a cohort of patients at risk for developing the disease."
Over a single decade, the incidence of liver cancer (hepatocellular carcinoma) increased from 1.8 to 2.5 per 100,000 patients, in large part due to a rise in the spread of hepatitis C virus.
"Hepatitis C has become a tremendous public health problem," explains co-senior author Nezam Afdhal, MD, Director of the Liver Center at BIDMC and Associate Professor of Medicine at Harvard Medical School. "And a significant number of hepatitis C-infected patients will go on to develop liver cirrhosis."
Cirrhosis results when healthy tissue is replaced by scar tissue, preventing the liver from properly functioning. Cirrhosis itself is responsible for more than 25,000 deaths each year. But, adds Afdhal, secondarily, cirrhosis greatly increases a person's chances of developing liver cancer.
"Each year, cirrhosis patients have a 2% to 5% chance that their condition will escalate to cancer," he explains. "And the problem is that, right now, there is no reliable means of detecting liver cancer at an early stage, when surgical treatment is an option. Typically by the time the disease is discovered, the cancer has advanced and treatment options become much more limited."
The best hope for early detection is cancer biomarkers, serum proteins found in altered amounts in blood or other body fluids. The current biomarker for liver cancer in clinical use is alpha fetoprotein (AFP). In many cases, patients with hepatitis C undergo routine monitoring for AFP levels as an indicator of whether tumors may have developed in their livers.
But, as Libermann explains, the AFP biomarker has a number of shortcomings, including false positives and false negatives. "AFP not only fails to detect many early tumors, but it also lacks specificity. Consequently, elevated AFP levels could be indicators of not only cancer, but also of other liver diseases or even benign conditions, while on the other hand, many patients with small tumors will test negative for AFP."
The authors therefore decided to evaluate the sensitivy and specificity of SELDI-TOF MS for the detection of liver cancer and to compare its effectiveness with AFP.
Examining serum samples of 92 patients, including 51 patients with liver cirrhosis and 41 patients with liver cancer, and among the cancer patients, individuals with both large and small (less than 2 cm) tumors, the investigators were able to identify an 11-protein signature that accurately discriminated between the cirrhosis and cancer patients, first in a training set (made up of 26 cirrhosis and 20 liver cancer patients), and then again in an independent validation set (consisting of 25 cirrhosis and 19 liver cancer patients). The resulting diagnostic value--74% sensitivity and 88% specificity--compared favorably with the diagnostic accuracy of AFP (73% sensitivity and 71% specificity) as well as with two other biomarkers currently in clinical development for liver cancer, AFP-L3 and PIVKA-IL.
"Most strikingly," notes Libermann, "in patients with small tumors (less than 2 cm), where AFP identified only three, and AFP-L3 and PIVKA-II only one each, the 11-protein signature correctly identified seven of eight patients at this early stage of disease.
"Biomarkers play a major role in all aspects of personalized medicine, not only in early disease detection, but also in outcome prediction and evaluation of therapeutic responses," he adds. "This study provides strong evidence that serum contains early detection biomarkers and supports the notion that a combination of multiple biomarkers may prove more effective than individual biomarkers for diagnosis of liver cancer, as well as other cancers."
This study was funded by grants from the National Institutes of Health.