Laser-induced fluorescence made simple: implications for the diagnosis and follow-up monitoring of basal cell carcinoma

Eleni Drakaki,Alexander J Stratigos,Christina Antoniou,Carmen Salavastru,Clio Dessinioti

doi:10.1117/1.jbo.19.3.030901

Abstract

Noninvasive treatments are increasingly being used for the management of basal cell carcinoma (BCC), the predominant type of nonmelanoma skin cancer, making the development of noninvasive diagnostic technologies highly relevant for clinical practice. Laser-induced fluorescence (LIF) spectroscopy emerges as an attractive diagnostic technique for the diagnosis and demarcation of BCC due to its noninvasiveness, high sensitivity, real-time measurements, and user-friendly methodology. LIF relies on the principle of differential fluorescence emission between abnormal and normal skin tissues (ex vivo and in vivo) in response to excitation by a specific wavelength of light. Fluorescence originates either from endogenous fluorophores (autofluorescence) or from exogenously administered fluorophores (photosensitizers). The measured optical properties and fluorophore contributions of normal skin and BCC are significantly different from each other and correlate well with tissue histology. Photodynamic diagnosis (PDD) is based on the visualization of a fluorophore, with the ability to accumulate in tumor tissue, by the use of fluorescence imaging. PDD may be used for detecting subclinical disease, determining surgical margins, and following-up patients for residual tumor or BCC relapse. In this review, we will present the basic principles of LIF and discuss its uses for the diagnosis, management, and follow-up of BCC.

Highlights

Nonmelanoma skin cancer (NMSC) is a term used to encompass skin cancer forms other than malignant melanoma, and it most commonly refers to squamous cell carcinoma (SCC) and basal cell carcinoma (BCC)
Photodynamic diagnosis (PDD) is a method for tumor demarcation that is based on the visualization of a fluorophore, with the ability to accumulate in tumor tissue, by the use of fluorescence imaging
The autofluorescence spectra of malignant tissues have usually very low intensity of fluorescence radiation emitted by endogenous fluorophores, above excitation of 300 nm.[3,15,34,36,53]

Summary

Introduction

Nonmelanoma skin cancer (NMSC) is a term used to encompass skin cancer forms other than malignant melanoma, and it most commonly refers to squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). The optimal management of skin cancer relies on early and accurate diagnosis, appropriate treatment, and monitoring for potential relapse. Noninvasive treatments are increasingly being used for the management of BCC. Recent advances in the molecular pathophysiology of BCC have opened the way for new exciting targeted therapies, including oral hedgehog signalling inhibitors, in order to avoid the need of extensive, repetitive, or mutilating surgery.[2] A plethora of new developments in optical imaging techniques is available for the noninvasive diagnosis (photodiagnosis) of NMSC including fluorescence, diffuse reflectance, Raman and near-infrared spectroscopies, optical coherence tomography, and multiphoton and confocal laser scanning microscopies.[3,4] More interestingly, optical methods are increasingly being used to monitor clearance of skin cancer after traditional treatments and screen for early relapse detection. We will present the basic principles of laserinduced fluorescence (LIF) for the management of BCC, and we will discuss its use in early and advanced BCC diagnosis, the

LIF: Basic Principles Made Simple

Laser-Induced Autofluorescence for the Diagnosis of BCC

PDD for BCC

Optimizing Results

Conclusions and Future Perspectives