Symptoms linked to tumor metabolism Ten to twenty percent of lung cancer patients experience symptoms or groups of symptoms (syndromes) in organs that are neither invaded by nor obstructed by the tumor. These findings are called paraneoplastic syndromes. In some instances they appear early in the development of lung cancer and might trigger early diagnosis.
Investigators believe paraneoplastic syndromes are caused by various substances released by tumors, such as hormones, ormone-like proteins, bioactivators called cytokines, proteins called antibodies released by white blood cells, or by differences in the availability of critical metabolic substances such as iron. Some paraneoplastic syndromes are rare. Some can be caused by other cancers or other illnesses in addition to lung cancer. Not all subtypes of lung cancer are capable of causing all of the paraneoplastic syndromes.
The most common paraneoplastic syndromes in nonsmall cell lung cancer patients are:
• Hypercalcemia (high blood calcium levels). Overstimulated parathyroid glands or cytokines released by the tumor such as tumor necrosis factor, interleukin-1, transforming growth factor alpha, and some prostaglandins might recruit too much calcium from bone into the blood. Another possible cause of hypercalcemia is invasion of bone by a tumor. The many symptoms associated
with hypercalcemia are described under “Endocrine syndromes” below.
• Excess growth of certain bones, especially in fingertips (hypertrophic osteoarthropathy)
• Blood clots
• Excess breast growth in men (gynecomastia)
The most common paraneoplastic syndromes in small cell lung cancer patients are:
• Syndrome of inappropriate antidiuretic hormone (SIADH), causing low blood levels of sodium.
SIADH is caused by secretion of antidiuretic hormone by the tumor. Antidiuretic hormone, also called vasopressin, acts on the idney to lower levels of sodium in the blood (hyponatremia). The many symptoms associated with SIADH are
described under “Endocrine syndromes” below.
• Blood clots
• Loss of balance and unsteady arm and leg motion
(cerebellar degeneration)