Palbociclib Combined With Afatinib for Advanced Squamous Carcinoma of Esophagus or Gastroesophageal Junction

Inclusion Criteria: Pathologically confirmed metastatic or inoperable locally advanced squamous carcinoma of the esophagus or gastroesophageal junction that is not amenable to radical radiotherapy. Prior progression to at least first-line chemotherapy which must include immune checkpoint inhibitors (except in patients with contraindications to immune checkpoint inhibitors). Adjuvant/neoadjuvant therapy is allowed and is considered first-line therapy for advanced disease if recurrence occurs during or within 6 months of completion of adjuvant/neoadjuvant therapy. At least one measurable tumor lesion according to RECIST V1.1 criteria. A lesion previously treated with radiotherapy is not acceptable as a target lesion unless the lesion is significantly progressive. Sign the informed consent form 18~75 years Performance status: ECOG 0-1 Good organ function: Blood routine: hemoglobin ≥90g/L, neutrophil ≥1.5×10^9/L, platelet ≥100×10^9/L; Renal function: creatinine≤1.5×upper limit of normal (UNL) or creatinine clearance ≥50ml/min; Liver function: total bilirubin (TBIL)≤1.5×upper limit of normal (UNL); ALT≤2.5×UNL, AST≤2.5×UNL; Ejection fraction at least 50% (or lower limit of normal) by echocardiogram Exclusion Criteria: Other pathological category, such as adenocarcinoma, adenosquamous carcinoma Have received CDK4/6 inhibitors or anti-EGFR targeted drugs in the past Known to have allergic reactions to any ingredients or excipients of experimental drugs Unable to swallow or under other circumstance which would drug absorption Other active malignant tumors, excluding those who have been disease free for more than 5 years or in situ cancer considered to have been cured by adequate treatment Diabetes was not controlled, defined as HbA1c > 7.5% after anti-diabetic drugs or hypertension was not controlled, defined as systolic / diastolic blood pressure > 140 / 90 mmHg after antihypertensive drug Myocardial infarction, severe/unstable angina, New York Heart Association (NYHA) class III or IV congestive heart failure in the past 12 months Known to be infected with human immunodeficiency virus (HIV), have acquired immunodeficiency syndrome (AIDS) related diseases, have active hepatitis B or hepatitis C Pregnant or nursing May increase the risk associated with participation in the study or administration of the study drug or mental illness that may interfere with the interpretation of research results There are other serious diseases that the researchers believe patients cannot be included in the study