The technology is based on a phenomenon called autofluorescence, explained by the Japanese research team as “the spontaneous emission of light that occurs when mitochondria, lysosomes, and other intracellular organelles absorb light”. Normal cells produce green autofluorescence in response to a certain type of blue light. But in mesothelioma and other cancer cells, the green autofluorescence is reduced and the light emitted shifts to a red-violet.
Doctors at the Department of Respiratory Center at Asahikawa Medical University in Hokkaido used this photodynamic diagnostic system to find tiny clusters of mesothelioma cells on the surface of the pleural lining during thoracic surgery. The researchers observed the predicted color shift in all of the tumors on the pleural surface, including mesothelioma tumors. Patients with lung cancer that had spread to the pleural surface also showed reduced autofluorescence. Just as importantly, cells from a non-malignant condition called pleural fibrous disease did not exhibit this change in autofluorescence.
Reporting in the Annals of Thoracic and Cardiovascular Surgery, the Japanese team’s lead author Masahiro Kitada concludes that the technology has merit in the management of malignant pleural mesothelioma. “Localization of pleural lesions by autofluorescence image was found to be useful,” he writes. In the case of patients with primary lung cancer Dr. Kitada suggests that the technology may even be used to help determine therapeutic strategies, including surgical approach.
A 2013 Turkish study on the value of autofluorescence in video-assisted thoracoscopic mesothelioma surgery also determined that it could be “useful” to detect small malignancies on the pleura that could not be diagnosed with white light alone.
Mesothelioma is considered one of the most challenging cancers to diagnose, particularly in its early stages. Definitive diagnosis usually requires a combination of methods, including history-taking to determine asbestos exposure, CT scanning, blood or effusion testing for biomarkers, and tissue biopsy.
Kitada, M et al, “Photodynamic Diagnoses of Malignant Pleural Diseases Using the Autofluorescence Imaging System”, Annals of Thoracic and Cardiovascular Surgery, August 20, 2014, Epub ahead of print
Liman, ST, et al, “Value of autofluorescence in video-assisted thoracoscopic surgery in pleural diseases”, The Thoracic and Cardiovascular Surgeon, June 2013, pp. 350-356