Radiation Therapy Side Effects
The side effects of Radiation Therapy can be classified as Acute, Subacute
Acute reactions occur during the course of treatment and are temporary.
They are manifested as signs of increased inter-cranal pressure or
worsening of neurological deficits. They results from an increase in cerebral
edema(abnormal accumulation of fluid). The administration of
corticosteroids usually decreases or alleviates symptoms. Steroids are
generally administered during the course of therapy to prevent this
occurrence. Other acute reactions are nausea, vomiting, anorexia(loss of
apetite), fatigue, alopecia(loss of hair) and skin irritation.
Subacute reactions generally develop one to three months after completion
of therapy. These are temporary in nature. Symptoms include anorexia(loss
of apetite), sleepiness, lethargy(drowsiness) and an increase in neurological
deficits. These effects result from the temporary disruption of myelin
formation, which helps speed the relay of nerve signals. It takes
approximately six weeks for myelin to repair.
Delayed reactions usally occur 6-24 months after completion of therapy.
These effects are irreversible and often progressive. They result from direct
injury to brain tissue and blood vessels. These reactions are due to changes
in the white matter and death of brain tissue caused by radiation-damaged
blood vessels. Symptoms vary from mild to severe decreased intellect,
memory impairment, confusion, personality changes and alteration of the
normal function of the area irradiated. Leukoencephalopathy(degeneration
of the white matter) occurs at the tumor site and surrounding irradiated brain.
The clinical manifestations range from mild cognitive neurological
impairment to dementia to death. Those at increased risk for long-term
radiation effects are children less than 2 and adults over 50 years of age.
Long-term effects can be initially managed to some degree with
corticosteroids and surgery to remove necrotic tissue. Other long-term
reactions include loss of vision, development of secondary
malignancies(oncogenesis) and pituitary-hypothalamic dysfunction(changes
in normal hormone levels)leading to problems with your thyroid, sugar
metabolism, fertility or ability to process water.
Chemotherapy Side Effects
Chemotherapy affects both normal and tumor cells. The effect on normal cells is the cause of side effects from chemotherapy. Some chemotherapy drugs do permeate(pass through) the blood brain barrier(the system that protects the brain from foreign substances like disease by blocking their passage from the blood). The group of drugs called nitrosoureas like Cisplatin, Cisplatinum or Carboplatin are such drugs and natural substances such as Taxol, also cross the barrier. Necrotizing Leukoencephalopathy is the form of diffuse white matter injury that follows chemotherapy, as well as a suppressed immune system.The body's immune system attacks and eliminates not only bacteria and other foreign substances but also cancer cells. Cancer cells are not foreign to the body but their biological function has been altered in that it doesn't respond to the body's normal mechanisms for controlling cell growth and reproduction. The abnormal cells can continue to grow, resulting in cancer. Much of the body's protection against cancer is carried out directly by cells of the immune system rather than by antibodies circulating in the bloodstream. Cancer is 100 times more likely to occur in people who take drugs that suppress the immune system than in people with normal immune systems.