Postoperative Diffusion-Weighted Imaging Hyperintensity Following Combined Photodynamic Diagnosis and Therapy Using 5-Aminolevulinic Acid and Talaporfin Sodium in Malignant Brain Tumors

Background/Objective: Intraoperative local photodynamic therapy (PDT) using talaporfin sodium (TS) and photodynamic diagnosis (PDD) with 5-aminolevulinic acid (5-ALA) are valuable adjuncts in the treatment of malignant brain tumors. Although their concomitant use was previously contraindicated due to photosensitivity concerns, a 2022 regulatory revision permitted their combined application. Transient postoperative hyperintensity on diffusion-weighted imaging (DWI) at the irradiation site serves as a biomarker for PDT effects, but the radiological and clinical impact of combining 5-ALA and TS remains unclarified. To compare and evaluate postoperative DWI findings and clinical outcomes in patients undergoing TS-PDT with or without concomitant 5-ALA-guided PDD. Methods: This retrospective study analyzed 34 patients with recurrent primary malignant brain tumors who underwent TS-PDT between January 2019 and November 2025. Patients were divided into a TS alone group (n = 19) and a TS + 5-ALA group (n = 15). Postoperative DWI hyperintensity thickness and minimum apparent diffusion coefficient (ADC) values at the laser irradiation site were measured. Adverse events including photosensitivity were also compared. Results: No significant differences were observed between the TS alone and TS + 5-ALA groups in DWI hyperintensity thickness (3.71 mm vs. 3.90 mm; p = 0.703 or median ADC values (601.0 × 10−6 mm2/s vs. 527.0 × 10−6 mm2/s; p = 0.205). Furthermore, there were no significant differences in the incidence of photosensitivity and liver enzyme elevation. Conclusion: Concomitant use of 5-ALA-PDD and TS-PDT can be used without worsening DWI findings at the PD laser irradiation site.