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Patients who have had one oral cancer are at increased risk of developing a further malignant tumour, the detection of which is made difficult (and is often delayed) by the innocuous appearance of the early oral lesion. A technique that could reliably detect early cancers would be useful to both oral and dental health specialists. We describe a pilot study in which we used a compact spectroscopic instrument designed to excite and measure fluorescence in the oral cavity. The data were processed using principal components analysis, and the results suggest that the technique might be valuable for detecting early oral cancers. Further work should be performed to investigate some unusual characteristics observed within our data to ascertain if these are significant, simply due to errors made due data collection, or are due to other lifestyle factors. Such work could also verify that the data are due to detection of ALA metabolite in cancer and not some other systemic effect.

Background: In recent years, 5-aminolaevulinic acid (ALA) has become an increasingly popular photosensitizing drug for use in both photodynamic therapy (PDT) and photodetection (PD) of cancers. ALA metabolizes within tissue to form the photosensitizer protoporphyrin IX (PpIX). Like most photosensitizers, PpIX is fluorescent, and this fluorescence progressively decreases during PDT. This phenomenon is referred to as photobleaching., Aim: Our aim in carrying out this experiment was twofold: firstly, to compare the relative capacity of red and blue light to cause photobleaching; and secondly, to compare the capacity of a fixed light dose to cause photobleaching, when delivered at different intensities., Method: In this paper, we describe the implementation of a compact fluorescence spectrometer in monitoring the photobleaching of ALA-induced PpIX in vivo on the skin of healthy volunteers., Results: We have been able to show that blue light causes more rapid photobleaching than red light, and that under illumination with red or blue light, delivery of a fixed light dose at a lower intensity results in more photobleaching., Conclusion: Comparison of the photobleaching rates suggests that a blue light intensity of 5 mW/cm(2) gives the same rate of photobleaching as the typical red light PDT intensity of 100 mW/cm(2). Further investigation of the correlation between PpIX photobleaching and PDT effect would be beneficial in interpreting the clinical significance of our findings.