Effect of photodynamic therapy for early gastric cancer with submucosal invasion

Abstract

Photodynamic therapy (PDT), which is the endoscopic method using hematoporphyrin derivative (HpD) as the photosensitizer and laser beam as the excitation light source, is regarded as a safe and promising method for treating early gastric cancer, because malignant tissue can be destroyed selectively. However, it was not certain that PDT was curative for early gastric cancer (EGC) with submucosal invasion, because transmissivity of light limits the depth of effectiveness. Then, we newly investigated an excimer dye laser (EDL) instead of an argon dye laser (ADL), because the EDL (specifications: wavelength: 630 nm; pulse energy: 4 mJ; peak power: 400 kW; pulse width: 10 nsec; frequency of repetition: 40 Hz) had higher transmissivity through the tissue, and more effective in photodynamic action than those of ADL. The procedure of PDT was as follows: (1) Two mg/kg of freeze-dried Photofrin II was injected intravenously; (2) About 50 hours later, the entire lesion plus a 5 mm width of marginal mucosa was irradiated with the EDL beam transmitted endoscopically. As a standard, the irradiation was delivered at a total dose of more than 60 joule/cm2; (3) After PDT, the patients were kept in bed with no food and were given continuous i. v. infusion of glucose and saline solution with an H₂-blocker and antibiotics for two days. In this study, from September 1990 until March 1993, eighteen cases of EGC, which consisted of 12 mucosal and 6 submucosal, were treated by PDT with EDL and freeze-dried Photofrin II. These patients could not be treated by operation because of high risk factors or old age. The response was evaluated by endoscopy with biopsy and cytology in the follow-up examinations.The rates of local cure were 100%(12/12) and 83%(5/6) for mucosal and submucosal carcinomas, respectively (Table 1). In the last study, between 1981 and 1990, we treated 37 EGC lesions by PDT with the ADL and Photofrin I/II, and evaluated them in the same standard as in this study. The rates of local cure were 59%(13/22) and 53%(8/15) for mucosal and submucosal carcinomas, respectively (Table 2). The relation between dose (J/cm2) and curability in PDT was examined, comparing EDL with ADL. In EDL, dose of 60J/cm2 was sufficient to obtain local cure in submucosal carcinomas, while in ADL, 90J/cm2 was required at least (Figure 1).