This project is a prospective, multicenter, single-arm, phase II clinical study aimed at evaluating the efficacy and safety of fecal microbiota transplantation (FMT) in treating advanced tumor cachexia.

This study intends to include 66 patients with advanced gastric cancer, colorectal cancer, and lung cancer suffering from cachexia (including the pre-cachexia stage and the cachexia stage), who have received second-line or higher treatment. The patients will undergo a 12-week intervention of fecal microbiota transplantation. Fecal microbiota capsules will be orally administered at three time points: Day 0, Day 28, and Day 56. Blood and fecal samples will be collected at three time points: Day 0, Day 28, and Day 84 for metagenomic and metabolomic testing. Abdominal weight will be measured at four time points: Day 0, Day 28, Day 56, and Day 84. The above time points can be advanced or postponed by up to 3 days. The FAACT A/CS anorexia assessment scale and the Brief Fatigue Scale will be filled out. Liver function and CRP will be tested. The primary endpoint is the change in body weight compared to the baseline at 12 weeks (Day 84). The secondary endpoints include: the improvement in albumin, prealbumin, CRP, appetite, and fatigue compared to the baseline at 12 weeks, as well as safety.

Inclusion Criteria:

1. Pre-advanced or advanced tumor cachexia stage.
2. Age ≥ 18 years old, ECOG score 0-2, expected survival > 3 months.
3. Patients with gastric cancer, colorectal cancer, or lung cancer who have received second-line or higher treatment.
4. No FMT treatment in the past six months.

Exclusion Criteria:

1. Any condition that affects gastrointestinal absorption, such as difficulty in swallowing, malabsorption, or uncontrollable vomiting; undergoing tube feeding or parenteral nutrition.
2. Neurotic anorexia, anorexia caused by mental illness, or difficulty in eating due to pain.
3. Acquired immunodeficiency syndrome.
4. Currently taking or planning to take other drugs that increase appetite or weight, such as adrenal corticosteroids (except for short-term use of dexamethasone during chemotherapy), androgens, progestogens, salidroside, olanzapine, and anamorin or other appetite stimulants.
5. Patients with Cushing's syndrome, adrenal or pituitary insufficiency; patients with difficult-to-control diabetes.
6. Current imaging or clinical manifestations of gastrointestinal obstruction.
7. Current uncontrolled coexisting diseases, including but not limited to decompensated cirrhosis, renal failure, uncontrolled metabolic disorders, severe active peptic ulcer disease or gastritis, or mental illnesses/societal conditions that may limit patient compliance with study requirements or affect the patient's ability to provide written informed consent.
8. Within 12 months prior to the first administration, there was unstable angina pectoris, myocardial infarction, congestive heart failure (grade 2 or above according to the New York Heart Association functional classification), or vascular diseases (such as aneurysms with a risk of rupture), or other cardiac damages that may affect the safety evaluation of the study drug (such as poorly controlled arrhythmias, myocardial ischemia); within 6 months prior to the first administration, there was esophageal-gastric varices, severe ulcers, gastrointestinal perforation and/or fistula history, history of gastrointestinal obstruction (including incomplete intestinal obstruction requiring parenteral nutrition), intra-abdominal abscess or history of acute gastrointestinal bleeding.
9. Within 4 weeks prior to the first administration, a serious infection occurred, including but not limited to conditions requiring hospitalization.