3.02] Non-invasive optical diagnostic methods – A possible aid for early tumor diagnosis in the upper aerodigestive tract

Abstract

Objective Unlike for other types of malignancies, the incidence and mortality rates of cancers of the upper aerodigestive tract (UADT) have been remaining static for the last decades. An improved early diagnosis of these malignant mucosal lesions and their precursors may help to lead to a reduction in both rates. It seems possible that this goal can be reached using a combination of non-invasive optical diagnostic methods. Material and methods Different optical methods were investigated in groups of patients (n=15–80) with, or at high risk of developing a mucosal malignancy of the UADT: autofluorescence imaging (AFI; n=80) and enhanced fluorescence imaging (EFI; n=79) using 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) as tools for optical screening; multiple fluorophore analysis (MFA; n=18) and elastic scattering spectroscopy (ESS; n=25) as “optical biopsy” methods; optical coherence tomography (OCT; n=34) as a method to investigate the depth of a lesion, i.e. to differentiate hyperplasia/dysplasia from early invasive cancer. Results When AFI or EFI was used in conjunction with conventional examination procedures, the detection of dysplastic or early malignant lesions was markedly improved (6 additional lesions for AFI vs. 7 for EFI). Additionally, the lesions were far easier to delineate against innocuous mucosa under fluorescence imaging. For both spectroscopic methods (MFA and ESS), it was possible to prove their feasibility to be able to differentiate between normal and cancerous mucosa (MFA: sensitivity 100%/specificity 94.4%; ESS: sensitivity 70.0%/specificity 78.8%). Using OCT, surface structures such as the keratin and epithelial layer, the epidermal–dermal junction and areas of cellular crowding were clearly identifiable and showed a good correlation to the histopathological slides to a depth of approximately 1.5 mm. Of 34 lesions investigated so far, 2 out of 2 early malignant lesions as well as 29 out of 32 non-/premalignant lesions could be correctly differentiated using OCT. Conclusion Even though the results are so far based on a very limited number of patients, the optical diagnostic methods presented here appear to be very helpful for the detection, differentiation and mapping of precancerous and early malignant mucosal lesions of the UADT. They hold great promise for improving early tumor diagnosis particularly when they are used in combination.