Megestrol acetate is primarily used in the treatment of breast and endometrial cancers. It works by altering the hormone levels in the body, thereby slowing the growth of certain types of cancer cells that require these hormones to multiply. Additionally, it is prescribed to manage appetite loss and severe weight loss in patients with AIDS, helping to improve their nutritional status and overall quality of life. In some cases, it is also used off-label to address cachexia, a condition characterized by extreme weight loss and muscle wasting, often associated with chronic diseases like cancer. Its ability to stimulate appetite and promote weight gain makes it a valuable option in palliative care settings.