Modelling novel PDT approaches to target peripheral lung cancers (Conference Presentation)

Abstract

While the prevalence of central bronchial tumours is declining, that of peripheral lung tumours is increasing. Peripheral lung tumours present either as individual index lesion or as field cancerization, requiring for the former targeting of particular confined volumes of lung tissue versus a therapy for an entire lung or particular lobes thereof. Using FullMonte, a Monte Carlo code; the ability to achieve a tumour selective PDT by transbronchial light source placement was simulated for 525, 665 and 808 nm wavelength. Simulations were executed utilizing in silica models with up to 10 generations of the bronchial tree, tissue photosensitizer concentrations taken from literature or measure in preclinical model systems and tissue optical properties measured with alive ex vivo pig and human lungs perfused with either blood or a transparent low cellular (STEEN) fluid. The measured effective attenuation coefficients [cm-1] at the three wavelengths for ventilated lungs with either blood 1.26±1.07, 1.93±0.534, 1.09±0.93 or STEEN fluid 1.01±0.873, 0.901±0.318, 0.641±0.31 used as perfusate. When modelling the PDT dose distribution in the lung’s the bronchial air ducts up to the eight generations perturb the fluence considerably. In all simulations, a dose sufficient to cause necrosis in 98% of the target volume placement of 3 source fibres albeit with various extent of normal lung tumour damage. Full coverage of an entire lung lobe with only three source fibres placed does not provide for effective coverage of the diffuse disease unless a very high selective uptake of the photosensitizer in malignant tissues can be achieved.