Apatinib Combined With S-1 in the Second-line Treatment of Advanced Pancreatic Cancer

Inclusion criteria: * 18-70 years old; * ECOG score: 0-2; * Have confirmed metastatic or locally advanced unresectable pancreatic cancer; * At least one measurable lesion according to the RECIST1.1 standard; * First-line chemotherapy drugs do not include S-1 or fluorouracil drugs; * Main organ functions meet the following standards: * Baseline blood routine (the inspection standard should meet the requirements of no blood transfusion and blood products within 14 days, no use of G-CSF and other hematopoietic stimulant correction) : * Hemoglobin\>80g/L * The absolute neutrophil count (ANC) 1.5 x 109 / L; * Blood platelet (PLT)\> 90 x 109 / L; * Baseline biochemical test shall meet the following standards: * T BIL \< 1.5\*ULN. * A LT and AST\<2.5\*ULN, and in patients with liver metastasis \< 5\*ULN; * Cr≤1.5\*ULN. * Albumin is greater than or equal to 30g/L; * Women of child-bearing age must already have access to reliable contraception. Pregnancy tests (serum or urine) were performed within 7 days prior to enrollment and the results were negative, and a reliable method of contraception was preferred 8 weeks after the trial period and the last drug administration; * Subjects will voluntarily join the study and sign the informed consent. Exclusion criteria: * Clearly allergic to apatinib, S-1 or their excipients; * There are various factors affecting oral drugs (including dysphagia, chronic diarrhea, intestinal obstruction, etc.); * Serious heart diseases in the last six months, including : * angina; * myocardial infarction; * heart failure; * interphase of QTc \>450ms; * any other heart diseases that were judged as unsuitable for the study; * Combined with uncontrollable hypertension after drug treatment (systolic blood pressure \>140mmHg, diastolic blood pressure \>90mmHg); * Complicated with other serious medical diseases, including cerebrovascular disease, uncontrolled infection, active peptic ulcer, intestinal obstruction, etc.; * Metastasis of tumor central nervous system; * Women during pregnancy and lactation; * The patient has been diagnosed with other tumors in the past five years, except for the following situations: B. Cured basal cell carcinoma of the skin and cured orthotopic carcinoma of the cervix; * The time from the last chemotherapy is shorter than 4 weeks or 5 half-life (the time taken is older), and the time from the last radiotherapy is shorter than 4 weeks; * Use the experimental drug within 28 days before enrollment; * Patients with grade 2 or above toxicity caused by the use of anti-tumor drugs before enrollment; * Have mental disorders or a history of substance abuse; * Other circumstances that the investigator deems inappropriate to participate in the study;