Liposomal Irinotecan and 5-FU as Second-line Therapy for Patients With ESCC

Inclusion Criteria: * Age: 18-75 years old. * Unresectable esophageal squamous cell carcinoma confirmed by histopathology and/or cytology. * Failure or intolerance to first-line treatment. * At least one measurable lesion (according to RECIST v1.1). * Eastern Cooperative Oncology Group (ECOG) performance status of 0 \~ 1. * The expected survival time ≥3 months. * Subject has adequate biological parameters as demonstrated by the following: absolute neutrophil count (ANC) ≥1.5×10\^9/L, platelet count ≥100×10\^9/L, hemoglobin (Hgb) ≥90 g/L. * Adequate hepatic function as evidenced by total bilirubin ≤1.5 × upper limit of normal (ULN), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤2.5 x ULN, ≤5 x ULN if liver metastases are present. Documented serum albumin ≥ 3 g/dL. * Adequate renal function as evidenced by serum creatinine (Cr)≤1.5 x ULN or creatinine clearance ≥60 mL/min. * Subjects agree to use contraception and are not pregnant or breastfeeding women. * Agree and be able to comply with the plan during the study period. Provide written informed consent before entering the study screening. Exclusion Criteria: * Any other malignancy within 5 years prior to randomization, with the exception of cured in-situ carcinoma or basal cell carcinoma. * Received irinotecan/irinotecan liposome based therapy in the first line. * Active, uncontrolled bacterial, viral, or fungal infections that require systemic treatment. * Active HIV infection. * Combined with uncontrollable systemic diseases, such as unstable angina, myocardial infarction, congestive heart failure, severe unstable ventricular arrhythmia, severe pericardial disease history and other cardiovascular diseases; uncontrolled hypertension(Defined as systolic blood pressure≥140 mmHg and/or diastolic blood pressure≥90 mmHg after treatment with standardized antihypertensive drugs), or history of critical hypertension, hypertensive encephalopathy; uncontrollable diabetes, etc. * Presence of severe gastrointestinal disease (including active bleeding, \> grade 1 obstruction , \> grade 1 diarrhea or gastrointestinal perforation) * Allergy to or intolerance to therapeutic drugs or their excipients. * Presence of central nervous system metastasis. * Use of strong inhibitors or inducers of CYP3A, CYP2C8 and UGT1A1. * Participated in other trial within 30 days or within 5 half-lives of the drug prior to the first dose of study treatment. * Patients who are not suitable to participate in this trial for any reason judged by the investigator.