Several optical imaging techniques have been developed to ease the burden of skin cancer disease on our health care system. Hyperspectral images can be used to identify biological tissues by their diffuse reflected spectra. In this second part of a three-phase pilot study, we used a novel hand-held SICSURFIS Spectral Imager with an adaptable field of view and target-wise selectable wavelength channels to provide detailed spectral and spatial data for lesions on complex surfaces. The hyperspectral images (33 wavelengths, 477–891 nm) provided photometric data through individually controlled illumination modules, enabling convolutional networks to utilise spectral, spatial, and skin-surface models for the analyses. In total, 42 lesions were studied: 7 melanomas, 13 pigmented and 7 intradermal nevi, 10 basal cell carcinomas, and 5 squamous cell carcinomas. All lesions were excised for histological analyses. A pixel-wise analysis provided map-like images and classified pigmented lesions with a sensitivity of 87% and a specificity of 93%, and 79% and 91%, respectively, for non-pigmented lesions. A majority voting analysis, which provided the most probable lesion diagnosis, diagnosed 41 of 42 lesions correctly. This pilot study indicates that our non-invasive hyperspectral imaging system, which involves shape and depth data analysed by convolutional neural networks, is feasible for differentiating between malignant and benign pigmented and non-pigmented skin tumours, even on complex skin surfaces.

Non-surgical treatments are cost-effective options for low-risk basal cell carcinomas (BCCs) i.e. superficial or small nodular BCCs located outside the high-risk locations. Hexyl aminolevulinate (HAL) and 5-aminolevulinic acid nanoemulsion (BF-200 ALA) with enhanced penetration depth enables the use of lower concentrations compared to methylaminolevulinate (MAL) in photodynamic therapy (PDT). We have previously reported comparable short-term efficacies for MAL 16%, BF-200 ALA 7.8% and HAL 2% in PDT of low-risk BCC, and here we report the long-term results. The goal of this trial was to compare long-term outcomes of HAL and BF-200 ALA, compared to MAL in PDT of low-risk BCCs. Ninety-eight histologically verified low-risk BCCs on the trunk or extremities were included and randomized into three arms to receive PDT in two sessions with MAL, BF-200 ALA or HAL. A blinded dermatologist assessed the response, cosmetic outcome, and obtained biopsies for histological verification at three months, one year and five years. Histologically verified non-responsive lesions were excised. Patients' satisfaction with the treatment was also queried. According to intention-to-treat (ITT) analyses, the cumulative response rate at one year was 90.6% for MAL, 81.3% for BF-200 ALA, and 75.8% for HAL, and correspondingly at five years 71.9%, 54.6% and 60.6%. There were no statistically significant differences between interventions and comparator. The overall cumulative response rate for PDT was 82.5% at one year and 62.2% at five, and 48.6% of the treatment failures were recorded at five years. The recurrent lesions were excised as second line treatment. No aggressive subtypes were reported, with only superficial or nodular growth in the final histopathological report. There were no significant differences in cosmetic outcome or patient satisfaction. This trial shows that HAL has potential for dermatological PDT. However, the long-term efficacy of PDT in the treatment of low-risk BCCs remains rather low.