This study aims to assess the impact of adding olanzapine to nutritional advice and standard anti-tumor therapy on the survival and safety of patients with locally advanced, unresectable or metastatic gastric cancer, esophageal cancer, hepato-pancreaticobiliary cancer, and lung cancer. Researchers seek to determine whether olanzapine can improve progression-free survival (PFS), overall survival (OS), and objective response rate (ORR) in advanced cancer patients who received standard anti-tumor therapy, and investigate the relationship between olanzapine-induced weight changes and patient survival.

This study is a prospective, randomized, multicenter, open-label clinical trial to evaluate the effect of olanzapine on survival in patients with locally advanced, unresectable, or metastatic gastric, esophageal, hepato-pancreaticobiliary, and lung cancer. Patients who meet the inclusion and exclusion criteria will be formally enrolled after screening and signing an informed consent form. Eligible patients will be dynamically randomized in a 1:1 ratio to either the Olanzapine + Nutritional advice + Standard anti-tumor treatment group (ONS group) or the Nutritional advice + Standard anti-tumor treatment group (NS group). The ONS group will receive olanzapine treatment orally until disease progression. Survival outcomes, including median PFS, OS, and ORR, will be monitored during treatment through follow-up assessments.

In addition, baseline and post-treatment weight data will be collected to assess the incidence of weight loss and changes in body mass index (BMI) among patients. Researchers will collect survey questionnaires and conduct blood analyses to evaluate improvements in other symptoms associated with olanzapine and changes in quality of life and inflammatory markers. Primary and secondary study outcomes and adverse events will be assessed.

Inclusion Criteria:

1. Aged 18 years or older;
2. Eastern Cooperative Oncology Group performance status of 0-3;
3. Stage III or IV inoperable or metastatic gastric cancer, esophageal cancer, hepato-pancreaticobiliary cancer and lung cancer confirmed by histology or cytology;
4. Subjected to palliative systemic chemotherapy, regardless of first-line or second-line treatment;
5. Expected survival ≥ 3 months;
6. The patient is eligible for oral administration without dietary restrictions;
7. Exhibits a favorable adherence to treatment and follow-up, demonstrates compliance with the research protocol, and willingly signs the informed consent form.

Exclusion Criteria:

1. Weight loss and gain may be attributed to alternative factors, such as edema or ascites;
2. Suffers from mental disorders or is under the medication of any antipsychotic or antidepressant drugs;
3. History of central nervous system disorders (such as brain metastasis, epilepsy;
4. Patients undergoing sustained administration of sedative medications or long-term hormonal therapy, individuals with chronic alcoholism, or those with substance dependence on medications;
5. Prohibition of Olanzapine Intake for Contraindicated Individuals;
6. History of clozapine-induced agranulocytosis because patients will be at increased risk for neutropenia with Olanzapine;
7. Uncontrolled diabetes mellitus and Uncontrolled seizure disorder;
8. Pregnant and Nursing women;
9. Exclusion criteria include active participation in another interventional clinical trial, ongoing involvement in an observational (noninterventional) clinical trial, or being in the survival follow-up phase of an interventional clinical trial;
10. Researchers posit that any condition deemed potentially harmful to the subjects or that might prevent subjects from meeting or adhering to the research requirements shall not be permissible for inclusion in this study.