Is there a difference in survival after photodynamic therapy of bile duct cancer depending on the sensitizer?

Introduction: Photodynamic therapy (PDT) has shown significant survival benefit in non-resectable bile duct cancer. Two different hematoporphyrin derivatives (HPD) are today in clinical use as photosensitizers, Photofrin II (PF2) and Photosan-3 (PS3). Apart from their variations in chemical structure, little is known about potential differences in clinical performance. We retrospectively evaluated the effectiveness and complication rate of both HPDs in the treatment of patients with advanced bile duct cancer.

Methods: In treatment group A we used Photosan-3 (2mg/kg body weight) as photosensitizer, in group B we used Photofrin II in equal dosage.

Each sensitizer was administered intravenously 48 hours before laser irradiation. Irradiation was performed with a 4cm quartz fibre and a diode laser system (635 nm wavelength; 1,1W, 220J/cm). All patients were provided with plastic stents bridging the irradiated segments of the biliary tree. Prophylactic antibiotic treatment was prescribed for two weeks. Light protection was disposed for 4–6 weeks.

Results: 16 patients received PS3 (11m/5 f, median age 67 y), 13 patients received PF2 (11m/2 f; median age 70 y). There was no significant difference in age, tumor stage, gender and number of PDT sessions in both groups. Median survival in group A was 690 days [448–931; 95% CI] as compared to 494 days [84–903; 95% CI] in group B with no significant difference (p=0,87). No substantial skin reaction was observed. There was no difference in the rate of post-treatment cholangitis (Group A: 26%, Group B: 23%, p=0,84).

Conclusion: The potential of photodynamic therapy to prolong survival in non resectable bile duct cancer does not depend on the hematoporphyrin derivative used as photosensitizer. Newly developed photosensitizing agents should combine a better anti-tumor activity with a reduced risk for infectious complications.

Keywords: Photodynamic therapy, bile duct cancer, cholangiocarcinoma, photosensitizer, hematoporphyrin