336. EFFICACY AND SAFETY OF PHOTODYNAMIC THERAPY FOR SECONDARY PRIMARY ESOPHAGEAL SQUAMOUS CELL CARCINOMA AFTER CHEMORADIOTHERAPY OR RADIOTHERAPY FOR ANOTHER MALIGNANCY

Abstract Background Photodynamic therapy (PDT) using talaporfin sodium is known as the effective, safe, and less invasive treatment for local failure after chemoradiotherapy (CRT) or radiotherapy (RT) for esophageal squamous cell carcinoma (ESCC). The secondary primary ESCC sometimes occur at different site after CRT/RT for ESCC or other cancer, and PDT may be considered for such lesion if endoscopic resection and surgery are not suitable for patients. However, the actual therapeutic efficacy remains unclear. This study aims to evaluate the efficacy and safety of PDT using talaporfin sodium for untreated secondary primary ESCC with a history of CRT/RT for another malignancy. Methods This retrospective study enrolled the patients underwent PDT using talaporfin sodium for untreated secondary primary ESCC in the treatment field of prior CRT/RT for another malignancy at the National Cancer Center Hospital East from September 2016 to October 2021. The inclusion criteria of PDT in this study were as follow; 1) invasion depth limited within T2, 2) <3/4 of the esophageal circumference, 3) absence of lymph node or distant metastasis, and 4) patient’s refusal or unsuitable physical condition for surgery. We evaluated the rate of local complete response (L-CR), incidence of adverse events, and clinical outcomes. Results Ten patients were enrolled in this study. Previous malignancy organ was hypopharynx (n=1), lung (n=2), and esophagus (n=7). All secondary primary ESCC were diagnosed as T1b. Finally, L-CR was achieved in 6 patients (L-CR rate: 60.0%). Among 6 patients with L-CR, one had local recurrence, one had lymph node recurrence, and the remaining four had no recurrence. During the median follow-up of 27.5 months, one patient with L-CR died from other diseases. Adverse events included grade ≤2 esophageal pain in 2 patients, photosensitivity and esophageal stricture in each one, and no esophageal perforation or treatment-related death. Conclusion As retreatment with RT is not available, PDT may be the treatment options for the secondary primary ESCC after CRT/RT for another malignancy.