AbstractsMedical & Health Science

ABSTRACT Background and purpose: As the skin cancer burden continues to increase, there is an urgent need for novel methods for the early detection of skin cancers, and for new cost-effective treatments. The hyperspectral imaging system (HIS) is a novel technique which offers the dual advantages of allowing the imaging of large skin areas rapidly and non-invasively. Daylight photodynamic therapy (DL-PDT), with the advantages of excellent tolerability and convenience, is an attaractive therapy for actinic keratoses (AK) and field cancerization.This thesis aimed to enable early and effective treatment of common premalignancies of photo-damaged skin.The first purpose of this thesis was to evaluate the feasibility of HIS in the detection of field cancerized skin and in the detection of ill-defined borders of lentigo maligna (LM) and lentigo maligna melanoma (LMM). In addition, this thesis aimed to further develop the treatment of field cancerized skin with photodynamic therapy using a novel photosensitizer in combination with daylight (DL-PDT), and to evaluate the cost-effectiveness of DL-PDT. Methods: This thesis included four non-sponsored prospective clinical studies. The novel prototype HIS, used in studies I-II, was developed for the study at the VTT Technical Research Centre of Finland. The technique enabled in vivo imaging of the skin prior to surgical procedures and produced abundance maps of the affected skin areas. The results were verified by histopathology. Study III was randomized double-blinded intra-individual split-face trial comparing novel photosensitizer formulation, 5-aminolaevulinate nanoemulsion (BF-200 ALA) with methyl-5-aminolaevulinate (MAL) in DL-PDT of AKs. In addition to blinded clinical and histological treatment efficacy, tolerability of the treatment was assessed. Study IV evaluated the cost-effectiveness of MAL-DL-PDT compared to conventional MAL-LED-PDT. Results: In studies I-II HIS showed its feasibility in both the detection of subclinical borders of ill-defined lentigo malignas (LM) and lentigo maligna melanomas (LMM), and in the detection of early subclinical actinic keratoses (AK). In study I HIS accurately detected 20 of 23 (87%) of the LM/LMM borders as confirmed by histology. HIS was useful i.e. detected the lesion borders more accurately than a clinician using Wood s light in 11 of 23 (47.8%) cases. Six re-excisions could have been avoided with HIS. In 3/23 cases (13%) HIS was not in concordance with the histopathology, which in two cases HIS showed lesion extension which was not verified histologically (wrong positive) and in one case HIS missed the subclinical extension (wrong negative). In study II with 12 patients and 52 clinical AKs, HIS accurately detected all the clinical lesions in addition to numerous areas of subclinical damage. HIS findings matched the histopathological findings in all 33 biopsied areas (AK, n=28, photo-damaged skin, n=5), revealing 16 subclinical lesions of which 10 were not detected by fluorescence diagnosis. In study III (13 patients, 177…