Last month, a professor at the University of Calgary questioned the validity of a report of the number of asbestos-related workplace deaths in Alberta, Canada. One reason the numbers are low, he claims, is that mesothelioma cases are under-reported. However, a clinical trial designed to test CT as a mesothelioma screening tool may lead to improved reporting.
In a July 16 CBCNews article, Professor Alain Tremblay of the University of Calgary’s Cumming School of Medicine said the Worker’s Compensation Board that claims 19 of 24 workplace deaths were attributable to asbestos exposure was incorrect. Tremblay says that often workers cannot prove their cancer was caused by asbestos, as many workers also smoked.
“If you look at cancer rates using government of Canada data, we know that rates of Mesothelioma are a fair bit higher,” says Tremblay. “For example, in Alberta we see about 50 cases of Mesothelioma per year.”
Tremblay, added, however, that the rate of mesothelioma cases should begin declining over the next 10 to 30 years.
Mesothelioma is caused by past exposure to asbestos and is most often found in trade workers such as insulators, plumbers and pipefitters, electricians, sheet metal workers, auto mechanics, refinery and factory workers and shipyard workers. Mesothelioma has an extended latency or incubation period and strikes decades after exposure to asbestos making it difficult to accurately diagnose.
However, now a clinical trial being conducted by researchers from the University of Calgary may be able to distinguish cancers caused by asbestos exposure in patients who have a history of asbestos exposure (at least 20 years ago) and present with pleural plaques (fibrous thickening of the lining of the lungs). The researchers report that although occupational exposure to asbestos is known to increase the risk of developing mesothelioma, “there is no accepted tool for the early diagnosis of mesothelioma or lung cancer in asbestos-exposed subjects available.”
Through “serially” imaging the pleural plaques using low-dose CT, the study will quantify the individual and overall volume and compute growth rate with time, ultimately identifying “the presence of mesothelioma early, before symptoms occur.”
Participants in the trial will undergo an initial CT. If pleural plaques are seen, a follow up CT will be conducted at three or six months, with additional CTs scheduled later as determined. In addition, a blood sample will be secured to test for markers known to indicate mesothelioma or lung cancer. Biomarkers are used for both diagnosis and for developing treatment protocols for mesothelioma patients.
“Symptoms are subtle and non-specific, diagnosis is often late and the prognosis consequently is dismal,” for mesothelioma patients, according to the trial researchers.
Finding an early detection tool for mesothelioma can lead to improved survival. Nearly 3,000 Americans and over 500 Canadians are diagnosed with the terminal cancer each year.
For information about the clinical trial see ClinicalTrials.gov.