Monitoring of photobleaching in photodynamic therapy using fluorescence spectroscopy.

Photodynamic therapy (PDT) utilizing aminolevulinic acid (ALA) as a photosensitiser has been used to ablate premalignant/malignant skin conditions including superficial basal cell carcinoma (BCC) with acceptable cosmetic outcome. Clinicians continue however to face difficulties in determining the exact dose that is sufficient to achieve a complete healing from the condition where the experience of the clinician remains the only determinant factor. This inaccuracy sometimes leads to undertreating these lesions. Here, we have clinically evaluated the use of fluorescence imaging system as monitor of protoporphyrin IX (PpIX) photobleaching in patients with BCC and compares this to the clinical outcome. Four readings were acquired from each patient (n=14) "pre-PDT", "peri-PDT" (333secs), "peri-PDT" (660secs) and post-PDT. It was found that red fluorescence values decreased markedly during PDT, and considered to be significant when compared to pre-PDT (P = 0.0018) and post- PDT (P = 0.0025). The red fluorescence value in pre-PDT was found to be higher in BCC of cheek and scalp (where the response rate, RR = 100%) in comparison to the temple (RR = 75%) and nose (RR = 33%). By comparison, the post- PDT red fluorescence values in cheek and scalp were lower than that of the temple and nose, respectively; this may be a useful indicative of the response rate of tissue to therapy.

Photodynamic therapy down-regulates the invasion promoting factors in human oral cancer.

Squamous cell carcinomas of the head and neck are characterized by their high tendency for invasion and metastasis. Several studies have identified the roles of matrix metalloproteinases (MMPs), vascular endothelial growth factors (VEGF) and urokinase plasminogen activators (uPA) in this process. Photodynamic Therapy (PDT) is an emerging treatment currently in clinical practice for the treatment of early cancer. Here we evaluate, in vitro, the influence of PDT on the expression of these molecules. A series of human keratinocyte cell lines derived from human oral squamous cell carcinomas (OSCC) were used as the PDT 'targets' in this study. Each cell line was subjected to sublethal dose of PDT. Activity of MMP-2, MMP-9, MMP-13, uPA and VEGF were evaluated at protein levels using zymography and ELISA on culture medium. For uPA, a chromogenic assay was performed. Gelatin zymography results revealed that, in control medium, MMP-9 and MMP-2 were secreted in proform. MMP-2 was highly expressed by H376 cells while VB6 and UP cells relatively show similar MMP-2 with comparatively low expression. For MMP-9, the latent type was highly expressed by VB6 cells and only slightly by H376, while active-MMP-9 was expressed by VB6 cell line only. Following PDT, both active and latent MMP-2 and MMP-9 were down regulated by UP and VB6 cells (p<0.001), while H376 showed an increase in active-MMP-2. These observations were supported by ELISA. This study has demonstrated that, PDT causes the suppression of factors responsible for tumour invasion which may be of therapeutic value.

Fluorescence spectroscopy combined with 5-aminolevulinic acid-induced protoporphyrin IX fluorescence in detecting oral premalignancy.

BACKGROUND: Early detection of premalignant/malignant lesions in the oral cavity can certainly improve the patient's prognosis. This study presents fluorescence imaging with the topical application of 5-aminolevulinic as a way to improve detection of various oral tissue pathologies. This procedure depends mainly on comparing the intensity of red and green fluorescence emitted from tissues during examination. MATERIALS AND METHODS: Seventy-one patients who presented with clinically suspicious oral leukoplakia were recruited for this study. Each of the patients was required to have 5-aminolevulinic acid in the form of mouth rinse prior to fluorescence imaging. Following this a surgical biopsy was acquired from the exact examination site. The results of the fluorescence spectroscopy have been compared with histopathology. RESULTS: A Student's t-test was applied to test the viability of the ratio between red and green fluorescence. The red-to-green ratio was found to increase significantly when the lesion was identified as dysplastic or carcinoma in situ. By applying a threshold line to discriminate between normal and dysplastic lesions; a sensitivity of 83-90% and specificity of 79-89% were obtained. CONCLUSION: Fluorescence spectroscopy combined with 5-aminolevulinic acid-induced protoporphyrin IX was found as a valuable tool in the diagnosis of oral premalignancy. This technique offers the potential to be advantageous over other non-optical techniques in terms of providing real-time diagnosis, in situ monitoring, cost effectiveness and more tolerated by patient compared to surgical biopsy.

Assessment of oral premalignancy using elastic scattering spectroscopy.

Optical spectroscopy systems have been involved in various clinical fields; however the main interest is still in the diagnosis of premalignant/malignant lesions. The aim of this study was to compare findings of Elastic Scattering Spectroscopy (ESS) with histopathology of oral tissues to see if this technique could be used as an adjunct or alternative to histopathology in identifying dysplasia. The technique involves the use of Mie scattering and is a simple non-invasive method of tissue interrogation. Twenty-five oral sites from 25 patients who presented with oral leukoplakia were examined by ESS using a pulsed xenon-arc lamp. Surgical biopsies were acquired from each of the examination sites. The results of the acquired spectra were then compared with histopathology. Two sets of spectra were obtained, and by using a linear discriminant analysis, a sensitivity of 72% and a specificity of 75% were obtained. These results are promising and could suggest that ESS may be able to identify dysplasia in oral tissues. To prove the usefulness of the ESS in dysplasia detection in oral tissues conclusively, a larger body of data is needed. We aim to continue this study to obtain more data in an attempt to increase the accuracy of the technique. Large, multi-centre trails are needed for each anatomical site, in order to gather more information about the differences between normal and dysplastic tissue.