Endobronchial photodynamic therapy under fluorescence control: Photodynamic theranostics.

Background: Photodynamic therapy (PDT) has several advantages. However, one of the disadvantages is its inability to be individualized according to biological characteristics of malignant tumors. The objective of this study was to investigate a strategy for individualized endobronchial PDT in the treatment of centrally located non-small cell lung cancer.

Methods: New approach suggests taking fluorescence-based measurements of chlorine E6 photosensitizer (PS) accumulation in the malignant tumor tissue, and assess PS consumption rate during PDT. Two randomized groups of 45 patients took part in the comparative study of standard PDT procedure, 662nm, pulse-periodic mode, therapeutic light (reference group - RG) versus the investigated individualized approach under fluorescence control after irradiation with violet light, 408nm, diagnostic light (study group - SG). The PDT-treatment parameters and results of follow-up bronchoscopy were compared between the groups.

Results: 43 (96%) of 45 patients in SG demonstrated intense fluorescence in the area of the tracheal/bronchial tumor stenosis. 4 (9%) of 45 patients (SG) demonstrated fluorescence of mucosa areas distant from the main tumor lesion after violet light irradiation. Mean fluence during the whole PDT procedure was 95±20J/cm (range 60-130J/cm), which was significantly lower than in RG (p=0.01). Total exposure time was significantly lower in SG (365±65s), compared with RG (690±65s), P=0.001. According to the follow-up bronchoscopy the difference in the PDT-treatment results between the groups is statistically insignificant.

Conclusions: The investigated strategy suggests using fluorescence control of the efficacy of PDT-treatment (photodynamic theranostics) to optimize and individualize the PDT procedure.