Why can unexplained weight loss occur with lung cancer?

Unexplained weight loss in patients with lung cancer is a common systemic effect, particularly as the disease reaches advanced stages. This phenomenon is often associated with a condition known as body wasting, which may be accompanied by a loss of appetite, or anorexia.123

The underlying mechanism for this wasting is likely driven by chemical mediators, such as tumor necrosis factor-alpha. This molecule can be secreted directly by tumor cells or produced by immune cells called macrophages in response to the malignancy. While weight loss is a recognized symptom of lung cancer, it is important to note that symptoms of the disease often do not manifest until the cancer has reached an advanced stage or has spread to other parts of the body.213