Examining tumor cells under a microscope is currently the only way to definitively diagnose malignant pleural mesothelioma. However, because getting a cell sample means that a patient has to undergo surgery, doctors typically use non-invasive tests like CT first. CT scans have become an important part of the diagnostic process for malignant pleural mesothelioma.
To see how valuable these tests really are for respiratory patients, experts from the Oxford Centre for Respiratory Medicine and the Lancashire Chest Centre in Preston, UK analyzed the CT scans and final diagnoses of 370 patients. All of the patients had symptoms consistent with pleural malignancies like mesothelioma had CT scans prior to thoracoscopic biopsies between 2008 and 2013.
Of the 370 suspected cancer cases, 211 (57%) were found to have mesothelioma or another kind of cancer when their tumor cells were examined. However, only 144 of these cases were determined to be malignant by CT scan – a sensitivity of 68%.
The researchers found that CT scans were more accurate at ruling out cancer in people thought to have a pleural malignancy, though still far from perfect . Of the 159 patients who were, in fact, cancer free, 124 had benign CT scans. This means that CT scans were 78% accurate at determining whether a set of symptoms was not caused by cancer.
“A significant proportion of patients being investigated for malignant disease will have malignancy despite a negative CT report,” writes lead investigator Dr. Rob Hallifax of the Oxford Respiratory Trials Unit in the journal Thorax. In these cases, mesothelioma diagnosis may be delayed until symptoms worsen, by which time treatment is less likely to be effective.
The study calls on the medical community to “re-evaluate” the heavy reliance on CT as a basis for deciding whether or not to perform a surgical biopsy on patients with suspected pleural cancers like mesothelioma. “Further studies to define the diagnostic pathway are now required,” writes Dr. Hallifax.
Approximately 2,500 people are diagnosed with mesothelioma each year in the UK – about the same number as in the US. Most of them develop the disease after many years of workplace exposure to asbestos.
Hallifax, RJ et al, “Role of CT in assessing pleural malignant prior to thoracoscopy”, July 30, 2014, Thorax, Epub ahead of print