Fluorescent Monitoring of Photodynamic Therapy for Skin Cancer in Clinical Practice

Abstract

The aim of the investigation was to assess the fluorescent imaging capabilities to monitor photodynamic therapy (PDT) of non-melanoma skin cancer, and study the correlation of PS (photosensitizer) fluorescence value (accumulation and photobleaching rate) and efficacy of the treatment provided. Materials and Methods. The study was conducted in the Nizhny Novgorod Regional Oncologic Hospital. We analyzed fluorescent images and PDT outcomes in 226 patients with non-melanoma skin carcinomas. Results. The assessment of short-term treatment results revealed the relationship between PS photobleaching and tumor complete response rate: a complete response was found in 89% cases in complete photobleaching, in 87% cases — in partial photobleaching, and in 81% — in no photobleaching (p>0.05). However, we found no effect of PS accumulation rate on complete response rate. The analysis of long-term results with significant difference (p=0.044) showed tumor recurrence rate in low PS concentration (tumor/norm) to be 9.5%, while in moderate and high concentrations the recurrence rate appeared to be 4.1%. There was revealed the tendency for recurrence rate increase — 10.4% with no PS photobleaching versus 4.4% in PS complete and partial photobleaching (p=0.051). The patients with high accumulation rate and complete PS photobleaching had the best clinical findings, the observation period being from 4 to 40 months. Conclusion. Fluorescent monitoring enables to maintain noninvasive control of PS accumulation and photobleaching that can contribute to the selection of individual laser exposure parameters. It is reasonable to develop multimodal bioimaging for follow-up real-time monitoring of basic photodynamic reactions and treatment results.