BRONCHOGRAPHY WITH HYTRAST

Novel light delivery method for performing transbronchial photodynamic therapy ablation to treat peripheral lung cancer: A pilot study

BACKGROUND

Photodynamic therapy involves using a photosensitizer with l illumination and is recommended for treating early, centrally located lung cancers, but it is not a standard treatment for peripheral lung tumor.. We previously proposed a novel light delivery method, in which lipiodol is perfused into the bronchial tree to increase the scope of illumination via the fiber effect. Herein, we attempted this novel technique under electromagnetic bronchoscope guidance in a hybrid operation room where lipiodol facilitated light diffusion, and evaluated the effectiveness and feasibility of this technique for peripheral lung cancers.

METHODS

This phase 0 pilot study included three patients with peripheral lung cancers (primary tumors ≤20-mm diameter). The photodynamic therapy was administered using Porfimer sodium as the photosensitizer, and an electromagnetic navigation bronchoscope in a hybrid operating room to guide the catheter to the tumor. This facilitated lipiodol infusion to encase the tumor and permit the transbronchial photodynamic therapy ablation.

RESULTS

Administering 630 nm 200 J/cm (400mW/500sec) energy through a 3-cm cylindrical diffusing laser fiber was safe; no significant acute complications were observed. Although the treatment outcome was unsatisfactory due to the low light dose, tumor pathology in one case revealed tumor necrosis, with no significant damage to the surrounding lung tissue.

CONCLUSIONS

Novel light delivery transbronchial photodynamic therapy ablation for peripheral lung tumors is feasible and safe. Additional clinical trials may help determine the best illumination plan and light dose through multiple deliveries from multiple angles.

Bronchoscopic light delivery method for peripheral lung cancer photodynamic therapy

Background

Trans-bronchoscope treatment for early stage small peripheral lung cancer, such as photodynamic therapy (PDT), has been investigated. However, despite the efficacy of PDT, light delivery issues limit its application. A method of administering mineral oil with a high refractive index (RI) was previously proposed to enhance light delivery in branched or bent anatomic structures. Lipiodol has a high RI and an exhaustive history of use as a contrast medium for bronchography. We aimed to determine whether the use of lipiodol, like mineral oil, could enhance the illumination effect and therapeutic range of PDT for peripheral lung tumors.

Methods

We injected lipiodol into a pig lung model, guided by a bronchoscope under fluorescent surveillance, to simulate future treatment in humans, and then illuminated with PDT laser fiber to the lipiodol-infused lung to test the technique feasibility in a pig orally administered 20 mg/kg of 5-aminolevulinicc acid (5-ALA) 2 hours before treatment. We also attempted to determine the maximal tolerable light dose in this pilot study for the future studies in human.

Results

We successfully injected lipiodol into peripheral lungs by this technique. The pig could tolerate up to a total of 40 mL of lipiodol and 800 J of red light, without severe acute fetal injury in a non-cancerous lung.

Conclusions

The technique of injecting lipiodol using bronchoscopy under fluorescent guidance was feasible in a pig model. We can apply the guide sheath through bronchoscopy under fluoroscope inspection. Lipiodol can be used as a light diffuser for the peripheral lung tumor PDT model. No severe lethal acute lung injury was caused by this PDT model under careful manipulation. Additional studies evaluating the dose correlation of the photosensitizer and light are needed.

Pulmonary reaction to Hytrast

Hytrast, a new bronchographic medium of high iodine content, provides excellent radiographic contrast. A number of clinical, pathological, and experimental studies have revealed inflammatory changes after pulmonary retention of Hytrast. Examination of 43 unselected pneumonectomy specimens after Hytrast bronchography revealed typical crystals in 15 instances. The pulmonary reaction included macrophage and foreign body giant cell accumulation, neutrophil leucocyte exudation, and fibrosis within terminal bronchioles and alveoli. It was concluded that these changes were associated with Hytrast retention.