Conversion from radical esophagectomy to definitive chemoradiotherapy after neoadjuvant chemotherapy for advanced esophageal squamous cell carcinoma: Treatment options based on chemotherapy response.

408 Background: Radical esophagectomy after neoadjuvant chemotherapy (NAC) is the established strategy for resectable advanced esophageal cancer. However, some patients convert to definitive chemoradiotherapy (dCRT) after NAC due to reasons such as their wishes or disease progression, and their prognosis remains uncertain. We aimed to investigate the prognosis of patients who converted to dCRT. Methods: Patients who underwent NAC for resectable advanced esophageal squamous cell carcinoma between 2006 and 2020 were enrolled retrospectively. The prognostic impact of subsequent treatment after NAC, planned surgery or conversion to dCRT, was compared. Results: We analyzed 686 patients, 70 who converted to dCRT (dCRT group) and 616 who underwent surgery (Surg group). The dCRT group had a poorer prognosis than the Surg group, with more advanced tumors and poorer response to NAC. Therefore, further analysis was conducted by categorizing patients as Responders (complete or partial response) and Non-responders (stable or progressive disease) to NAC. Among Responders in the dCRT group, 76.7% achieved a complete response, and the 5-year esophageal preservation survival rate was 66.9%. The 5-year survival rates for Responders were 77.5% and 71.3% in the dCRT and Surg groups. Multivariable analysis showed that dCRT did not worsen prognosis ( P = .706, hazard ratio = 1.13; 95% confidence interval, 0.59 to 2.16). Conversely, in Non-responders, dCRT had a significantly poorer prognosis, with 5-year survival rates of 22.3% and 45.1% in the dCRT and the Surg groups (P < .001). Conclusions: For patients responding to NAC, conversion to dCRT is considered a potential treatment option. The possibility of chemoselection has been suggested in the choice of treatment for esophageal squamous cell carcinoma.