Clinical Practice of Photodynamic Therapy Using Talaporfin Sodium for Esophageal Cancer

Abstract

Photodynamic therapy (PDT) using a conventional photosensitizer was approved for esophageal cancer in the early 1990s; however, it was replaced by other conventional treatment modalities in clinical practice because of the high frequency of cutaneous phototoxicity and esophageal stricture after the procedure. The second-generation photosensitizer, talaporfin sodium, which features more rapid clearance from the body, was developed to reduce skin phototoxicity, and talaporfin sodium can be excited at longer-wavelength lights comparing with a conventional photosensitizer. Endoscopic PDT using talaporfin sodium was initially developed for the curative treatment of central-type early lung cancer in Japan, and was approved in the early 2000s. After preclinical experiments, PDT using talaporfin sodium was investigated for patients with local failure after chemoradiotherapy, which was the most serious unmet need in the practice of esophageal cancer. According to the favorable results of a multi-institutional clinical trial, PDT using talaporfin sodium was approved as an endoscopic salvage treatment for patients with local failure after chemoradiotherapy for esophageal cancer. While PDT using talaporfin sodium is gradually spreading in clinical practice, further evaluation at the point of clinical benefit is necessary to determine the importance of PDT in the treatment of esophageal cancer.

Keywords: esophageal cancer; photodynamic therapy; talaporfin sodium.

Figure 1

Structural formula of talaporfin sodium.

Figure 2

The system of a diode laser which can excite talaporfin sodium.

Figure 3

A clinical flowchart for the indication of PDT using talaporfin sodium for esophageal cancer.

Figure 4

Endoscopic images of PDT procedure for local failure lesion after chemoradiotherapy for esophageal cancer. (a) The local failure lesion; we planned to illuminate laser the for two spots (yellow circles) to cover whole the lesion (identified with green arrows). (b) An opaque hood was attached at the tip of the endoscope to shield the surrounding mucosa during the illumination in order to avoid esophageal stricture. (c) The fluence of the diode laser at 100 J/cm² with a fluence rate of 150 mW/cm² was delivered through endoscopy, keeping a distance of less than 2 cm from the surface of the mucosa. (d) Endoscopic image a day after PDT showing the ischemic change at the laser-illuminated mucosa (identified with blue arrows).