The "Light Knife" for Gastric Cancer: Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) has been used clinically to treat cancer for more than 40 years. Some solid tumors, including esophageal cancer, lung cancer, head and neck cancer, cholangiocarcinoma, and bladder cancer, have been approved for and managed with PDT in many countries globally. Notably, PDT for gastric cancer (GC) has been reported less and is not currently included in the clinical diagnosis and treatment guidelines. However, PDT is a potential new therapeutic modality used for the management of GC, and its outcomes and realization are more and more encouraging. PDT has a pernicious effect on tumors at the irradiation site and can play a role in rapid tumor shrinkage when GC is combined with cardiac and pyloric obstruction. Furthermore, because of its ability to activate the immune system, it still has a specific effect on systemic metastatic lesions, and the adverse reactions are mild. In this Review, we provide an overview of the current application progress of PDT for GC; systematically elaborate on its principle, mechanism, and the application of a new photosensitizer in GC; and focus on the efficacy of PDT in GC and the prospect of combined use with other therapeutic methods to provide a theoretical basis for clinical application.

Keywords: chemotherapy; combination therapy; gastric cancer; immunotherapy; photodynamic therapy; photosensitizer; target therapy.

Figure 1

PDT-Induced Immune Effects.

Figure 2

Indocyanine green (ICG) near-infrared imaging for tumor and lymph node localization in laparoscopic radical gastrectomy. (A,B) arrow refers to the metastatic lymph nodes; (C–F) are ICG near-infrared light imaging of the lymph nodes behind the pancreas head, showing conventional cold light imaging, black and white mode, green mode, and color fluorescence mode, respectively.

Figure 3

A patient with AGC with pyloric obstruction received PDT. (A) Gastroscope shows tumor invasion from the lesser curvature to the pylorus, and the arrow indicates the pyloric stenosis; (B) PDT, the arrow points to the visible optical fiber inserted into the original stenosis (metal stent area), and the mucosa is white and necrotic after irradiation; (C) after one week of PDT, the local mucosa was gray and white, showing ischemic changes; (D) after one month of PDT, the lumen at the pylorus was unobstructed; (E) the tumor tissue from the anterior wall of the lesser curvature to the pylorus was smaller than before; (F) the lumen was still unobstructed after five months of PDT.

Figure 4

A patient with AGC receiving PDT. (A) Before treatment, atresia of the cardia can be seen; (B) it can be seen that the lumen is unobstructed after stent placement combined with PDT; (C) after one week of treatment, much gray-white necrotic tissue can be seen; (D) after three months of treatment, necrotic tissue can be seen to fall off, the lumen is unobstructed.