Thoracoscopic fluorescence diagnosis (TFD) of pleural malignancies: experimental studies.

Abstract

Fluorescence diagnosis (FD) using the photosensitiser 5-aminolaevulinic acid (ALA) was experimentally combined with conventional video assisted thoracic surgery (VATS) to improve tumour staging in advanced lung cancer with pleural tumour spread. A disseminated pleural carcinosis affecting the entire pleural cavity was induced by inoculation of human adenocarcinoma cells in nude rats. After 5-7 weeks of tumour growth the animals were randomised into six groups with different photosensitisation parameters. Pleural lavage was performed either with 1.5% or 3.0% ALA solution. Photosensitisation times varied were 2, 4, or 6 hours. Conventional white light VATS was first performed to evaluate tumour growth in the pleural cavity. Fluorescence illumination of the light source, the D-light, was then used to examine the site for additional tumours which were previously invisible. The tumour fluorescence intensity was measured spectrometrically and compared with normal tissue. Compared with conventional white light VATS alone, thoracoscopic fluorescence diagnosis (TFD) detected up to 30% additional pleural malignant lesions. The highest diagnostic sensitivity was reached 6 hours after 3.0% ALA pleural lavage. Photosensitiser accumulation in the tumour, measured indirectly by spectrometry, was up to 11 times higher than in normal tissue. TFD increases sensitivity of VATS for tumour staging. It may prevent unnecessary thoracotomies in cancer patients and facilitate surgical planning.