The efficacy and safety of conversion therapy after initial systemic chemotherapy in advanced esophageal cancer with distant metastases: A multicenter retrospective observational study.

310 Background: Systemic chemotherapy, with or without radiation, has been the standard treatment for esophageal squamous cell carcinoma (ESCC) with distant metastasis. The increased efficacy of multimodality treatment allows for the consideration of conversion therapy with curative intent for initially unresectable ESCC after initial treatment. In the present study, we examined the safety and effectiveness of conversion therapy for ESCC. Methods: Conversion therapy was defined as surgery or chemoradiation therapy (CRT) aiming at cure after initial treatment for tumors that were initially unresectable due to distant metastasis. The patients who underwent conversion therapy for ESCC between 2011 and 2021 at participating institutions were retrospectively reviewed. Patient backgrounds, treatment outcomes, and overall survival (OS) were evaluated. Results: From 22 institutions, 149 patients were enrolled. As defined, all patients received systemic chemotherapy as an initial treatment. The distant metastatic sites in para-aortic lymph nodes/extra regional mediastinal lymph nodes/lung/liver/bone/others were 81(54%)/19 (13%)/14 (9%)/11 (7%)/4 (3%)/20 (14%), respectively. After the initial treatment, 116 patients underwent surgery and 33 patients received CRT as conversion therapy. Of 116 patients who underwent conversion surgery, the incidence rate of postoperative pneumonia/leakage/recurrent laryngeal nerve palsy was 16%/7%/6%, respectively. R0 resection was obtained in 87%. Regarding the non-hematological toxicities during conversion CRT (CTCAE grade 3 or higher), decreased appetite/dysphagia/esophagitis was 21%/15%/9%, respectively. No grade 4 or higher hematologic toxicities were observed. The 3-year OS (3y-OS) rate for all patients was 41.9%; no significant differences were found between surgery and CRT groups (43.3% vs 37.0%, p = 0.112). Pathological responders showed a significantly longer OS than non-responders (3y-OS, 56.4% vs 36.1%, p = 0.010). The distribution or number of distant metastases were not identified as prognostic factors. Conclusions: This study showed that conversion therapy for ESCC patients with distant metastasis could be conducted safely and have a favorable prognosis. Since its survival benefit would depend on the pathological response, it is important to develop an indicator to predict pathological response before surgery and carefully select appropriate candidates of conversion therapy in ESCC.