397. TREATMENT OUTCOMES OF IMMUNE CHECKPOINT INHIBITORS AS PRIMARY THERAPY FOR UNRESECTABLE OR RECURRENT ESOPHAGEAL CANCER

Abstract Background For the primary treatment of unresectable or recurrent esophageal cancer, combination therapy with immune checkpoint inhibitors (ICI) such as pembrolizumab (Pem) with CF (cisplatin and 5-fluorouracil), nivolumab (Nivo) with CF, and Nivo with ipilimumab (Ipi) has been shown the significantly improve prognosis compared to standard CF therapy in international collaborative phase III trials. As a result, these ICIs have been approved as primary treatment agents in Japan, with treatment guidelines strongly recommending therapies including ICIs. We evaluated the treatment outcomes at our institute and discussed their utility. Methods We examined the treatment outcomes of 26 esophageal cancer patients who underwent primary treatment with Pem+CF, Nivo+CF, or Nivo+Ipi from January 2018 to January 2023. The median observation period was 7.0 months. Results There were 20 male and 6 female patients, with a median age of 69 years. Histologically, there were 24 cases of squamous cell carcinoma and 2 cases of adenocarcinoma. Of the 26 patients, 9 were postoperative recurrences and 17 were unresectable diseases. They were treated with Pem+CF (12 cases), Nivo+CF (7 cases), or Nivo+Ipi (7 cases) as primary therapy. The initial response was complete response (CR) in 1 case, partial response (PR) in 14 cases, stable disease (SD) in 2 cases, and progressive disease (PD) in 9 cases, resulting in an overall response rate of 57.6%. The median progression-free survival was 5.0 months, and the median overall survival was 15.2 months. There was no significant difference in prognosis according to the regimens. Grade 3 or higher adverse events included neutropenia in 3 cases, pituitary insufficiency in 1 case, and adrenal insufficiency in 1 case. One case with lung metastasis and two cases with para-aortic lymph node metastasis showed disappearance of metastatic lesions after chemotherapy including ICIs, leading to conversion esophagectomy. One case had anastomotic failure, but no other postoperative complications were observed. All patients are currently under observation without recurrence. Conclusion ICIs for unresectable or recurrent esophageal cancer showed a prolongation of prognosis in real-world clinical practice, suggesting their significance as part of a multimodal treatment approach including conversion surgery.