Cobalt is a nonradioactive metal found in nature from which radioactive isotopes can be produced by linear accelerators (for medical and commercial uses) and nuclear reactors (as a waste by-product). Cobalt-60 is the most common isotope and is widely utilized in medicine for the treatment of brain tumors and other central nervous system disorders.
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Cobalt-60 does emit radiation and must be handled with care. The side effects from exposure to this radioisotope depend largely upon the length of exposure and whether the exposure was internal (i.e. ingested or inhaled) or external (i.e. skin contact). These side effects may develop within hours or days of treatment (acute/subacute) or months and years later (delayed/late onset).
Cobalt-60 is almost exclusively used for Gamma Knife® surgery in the United States. The Gamma Knife® is a nonsurgical approach to the treatment of brain tumors, blood vessel abnormalities and other brain disorders, such as Parkinson’s disease, epilepsy and tremors. Multiple beams of gamma radiation from Cobalt-60 are directed simultaneously at a specific point in the brain. The delivery of a single, large dose of radiation (referred to as stereotactic radiosurgery), is executed with extreme precision and minimizes damage to surrounding healthy tissues.
Acute/Subacute Side Effects
Fatigue is the most common side effect of Cobalt-60 radiation and can last weeks to years. Many patients never regain their full energy, although it is not clear that radiation therapy alone is to blame, according to the American Cancer Society.
Cerebral edema, or swelling of brain tissue, occurs in all patients with varying degrees of severity. Some patients experience only a mild headache, while others can experience more significant headache, profound dizziness, nausea, vomiting and even loss of consciousness.
Localized hair loss-if the treated lesion was close to the scalp, skin irritation, scalp numbness/tingling, vision changes and decreased appetite have been reported.
Delayed/Late Onset Side Effects
Delayed or late onset symptoms can include slowed thinking, poor memory/recall, personality changes and confusion. The development of a new tumor--oncogenesis--is a rare occurrence from the radiation exposure in the brain.
Radiation necrosis, the death of brain tissue in response to radiation treatment, can also create an inflammatory reaction with symptoms of cerebral edema and can trigger seizures and rarely, death, according to the American Cancer Society.