Role of Bronchoscopic Photodynamic Therapy in Lung Cancer Management

Keyvan Moghissi

Disclosures

Curr Opin Pulm Med. 2004;10(4) 

In This Article

Abstract and Introduction

Purpose of Review: At present there is universal awareness of the role of photodynamic therapy in oncology. There is also a widespread acceptance of its safety and efficacy in its bronchoscopic application for bronchopulmonary malignant neoplasia. It, is therefore, both timely and relevant to present here the current status of bronchoscopic photodynamic therapy in lung cancer based on a critical review highlighting its indications and results.
Recent Findings: Bronchoscopic photodynamic therapy has emerged as an important treatment in lung cancer. In advanced disease with focus on quality of life, it offers palliation to all patients and survival benefit to a defined subset. In early cases it provides long survival (potential cure). In patients with intraepithelial stage disease, when it can be accurately diagnosed by the use of fluorescence bronchoscopy and endoscopic ultrasonography, the results can match those of surgical resection.
Summary: In bronchoscopic photodynamic therapy, the endobronchial tumor is presensitized by systemic administration of a sensitizing photochemical. After a time interval, bronchoscopic illumination (exposure to laser light) is performed to achieve cancer necrosis. The prerequisite for bronchoscopic photodynamic therapy is identification and histologic evidence of cancer within the airway. Photodynamic therapy is indicated in both early and advanced stage cancer. In patients with advanced disease and important exophytic tumors, the aim is palliation; in those with early central disease, treatment is done with curative intent. A large body of published evidence now suggests that these objectives are achievable.

Photodynamic therapy (PDT) uses a light-sensitive chemical (photosensitizer/drug), light of an appropriate wavelength, and oxygen that usually is available in the tissue environment. It is, in fact, an extension of phototherapy and photochemotherapy. Phototherapy uses light alone for treatment purposes and was the reason for the awarding of the Nobel Prize in medicine and physiology to Niels Ryberg Finsen in 1903.[1] Photochemotherapy uses a combination of a light-sensitive photochemical and light.

In PDT, the light-activated chemical requires molecular oxygen to achieve the photodynamic action (effect), which represents an end result of a chain of reaction that adversely affects the cell function and is expressed as necrosis.

Clinical PDT is a two-phase process. In the first phase, presensitization, the tissue to be treated (the target) is presensitized by a photosensitizer, which is administered topically or systemically. Photosensitizers have the ability of selective accumulation in tumor tissue with a high concentration ratio between target/normal cells. In the second phase, illumination, the presensitized tissue is exposed to the light whose wavelength matches the absorption band of the chemical photosensitizer. The interaction between the photosensitizer and the light, in the presence of oxygen, produces necrosis.

The mechanism of cell death in PDT is mediated by several events, among which are release of singlet oxygen and other cytotoxic species, direct cell injury, and vascular shutdown. More recently, the influence of inflammatory and immune responses have also been recognized.[2]

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