Safety and efficacy of conversion therapy for metastatic esophageal cancer: Exploratory analysis of JCOG1314.

401 Background: Patients with esophageal cancer (EC) with distant metastasis were treated with systemic chemotherapy. Recent advances in multimodal treatments have made conversion therapy (CT) a viable option for patients with metastatic EC. JCOG1314 was a randomized phase III trial to confirm the survival benefit of docetaxel plus cisplatin plus 5-fluorouracil (DCF) versus cisplatin plus 5-fluorouracil (CF) as initial treatment for unresectable or recurrent esophageal cancer. The purpose of this study was to evaluate the safety and survival impact of CT in patients enrolled in JCOG1314. Methods: CT was defined as surgery or chemoradiotherapy (CRT) aiming at cure after initial treatment for tumors that were initially unresectable due to distant metastasis. Clinicopathologic factors, surgical outcomes, toxicities during CRT, and survival were compared between CT and non-CT groups. CTCAE v4.0-JCOG was used to evaluate postoperative complications and adverse events during CRT. Results: Between September 2014 and April 2021, 240 patients were randomized to CF or DCF. Excluding patients with recurrent disease, 154 patients with initially unresectable esophageal cancer due to distant metastasis were selected for this study. Among them, 21 patients received CT which included conversion surgery (n=5) and conversion CRT (n=16). There was no significant difference in the number of metastatic organs, depth of invasion of the primary tumor, lymph node metastasis, and chemotherapy regiment between CT and non-CT groups. The most common M1 factor in CT group was the thoracic lymph node, followed by abdominal lymph node and cervical node. In conversion surgery group, there was no incidence of Grade 3 or higher pneumonia/leakage. Regarding the Grade 3 or higher non-hematological toxicities during conversion CRT, the incidence of appetite loss/ oral mucositis/pneumonia was 2 (13%)/2 (13%)/1 (6%), respectively. The 3-year overall survival (OS) of CT and non-CT groups was 52.4% and 14.3%, respectively. On multivariable analysis, patients with CT showed significantly better OS compared with the non-CT group (HR 0.36, 95% CI 0.19-0.67, p<0.01). In patients who underwent CT, there was no significant difference in OS between conversion surgery and CRT groups. Conclusions: This study demonstrated that CT was safely performed with favorable prognosis. A prospective study is warranted to investigate whether CT would improve survival in metastatic esophageal cancer.