This study is a prospective, real-world observational study. The objective is to evaluate the effectiveness and safety of nanocrystalline megestrol acetate in patients with cancer cachexia in real-world settings. Eligible participants were patients diagnosed with cancer cachexia who were scheduled to receive treatment with nanocrystalline megestrol acetate.

Inclusion Criteria:

• Patients with histologically and/or cytologically confirmed malignancy.
• Age ≥18 years at enrollment.
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2 and an expected survival of ≥3 months.
• Meeting the diagnostic criteria for cachexia (based on Fearon's criteria).
• Body mass index (BMI) ≤30.

Exclusion Criteria:

• Presence of any condition affecting gastrointestinal absorption, such as dysphagia, malabsorption, or uncontrolled vomiting; patients receiving tube feeding or parenteral nutrition.
• Presence of anorexia due to anorexia nervosa, psychiatric disorders, or pain that makes eating difficult.
• Patients with acquired immunodeficiency syndrome (AIDS).
• Currently receiving or planning to receive other medications that increase appetite or body weight, such as corticosteroids (except short-term dexamethasone during chemotherapy), androgens, progestins, thalidomide, olanzapine, anamorelin, or other appetite stimulants.
• Patients with Cushing's syndrome, adrenal or pituitary insufficiency, or poorly controlled diabetes mellitus.