Side Effects of Chemotherapy & Radiation Therapy

Radiation Therapy Side Effects

The side effects of Radiation Therapy can be classified as Acute, Subacute
and Delayed.

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.


Subacute and late effects of radiation on different organs.

In the months and years following exposure to large doses of
radiation, subacute and finally late effects of radiation injury
are seen. Cytologic atypia, which is likely to become less
prominent as the cells undergo successive divisions but
occasionally may lead to cancer, may be present along with
atrophy, infarction, ulceration, hemorrhage, inflammation, edema,
and scarring due in part to progressive stenosis of radiation
injured vessels, which become sclerotic and may accumulate foam
cells deep to the intima (considered almost pathognomonic of
radiation injury in the case of irradiated small vessels). To a
large extent, late effects of radiation on an organ may be
likened to diabetes, in which there also is progressive tissue
degeneration due to progressive ischemia from slowly degenerating
vessels, except that in the case of diabetes the injury is
systemic and not localized to the irradiated area. Epithelium in
irradiated tissue may vary from atrophic to hyperplastic over a
short distance. Telangiectatic vessels are frequently
encountered. Persistent round cell infiltration with a prominent
plasma cell component is very common. The slow destruction of an
irradiated organ may lead to death years after completion of the
therapy. These problems essentially place the radiation
therapist between a rock and a hard place, wishing to give
neither too little radiation and thus impair the chances for
curing a cancer, nor too much radiation with the risk of such
complications as pulmonary fibrosis, bowel wall injury, and
cerebral radionecrosis.

Neuropathy, a problem that sometimes occurs with chemotherapy treatment. It is damage to the nerves. It can occur from some chemotherapy drugs used in conventional cancer treatment.

There are three major goups of nerves in the human body, the peripheral nerves that carry information to and from the limbs, the nerves that supply the bowels and other internal organs, and the nerves of the head which connect to the ears, eyes, taste buds, etc. Nerves in any or all of these major groups can be affected by certain chemotherapy drugs.

Nerves are vulnerable to many kinds of damage. They can be damaged by certain cancers. This may be caused by the cancer cells producing a particular kind of biological agent that interferes with the function of the nerves. Sometimes, they can be damged by drugs used in chemotherapy treatment. The chemotherapy drugs that most likely cause nerve damage are the vinca alkaloids(vincristine, vindesine and vinblastine), platinum drugs(cisplatinum, carboplatinum) and the taxanes(taxol, taxotere). These drugs have the potential of interfering with nerve function.

You may notice symptoms in different areas of your body depending on which groups of nerves are affected. Symptoms in the hands and feet happen when peripheral nerve damage happens and are not rare with vinca alkaloids. The first sign of nerve damage is usually a feeling of tingling and numbness like what you experience when your foot goes to sleep after you've been sitting for a long time in an uncomfortable position. If the problem progresses further, it often produces weakness of the muscles, resulting in loss of strength at the wrist or the ankle. You will notice difficulty in doing up buttons and picking up coins. You may notice that you will tend to trip while walking up stairs or dragging your feet and tend to have a wide-based gait. In severe cases, the weakness may be so severe that you will need a wheelchair.

When the nerves in the bowel are affected, constipation is the earliest sign. In a few people, the abdomen becomes bloated with a distended bowel that is basically paralyzed. Some of the nerves in the head can also be affected. Platinum drugs can affect the auditory nerve and cause loss of hearing and tinnitus(ringing in the ears). Vision can very occasionally be affected.

A lot depends on how quickly your cancer treatment can be stopped. Sometimes the need for treatment is more urgent then the residual nerve damage. Sometimes, the balance between benefit from the drug and the side effect of nerve damage is more finely balanced.

Once treatment has been stopped, recovery is usually slow. It may take months to get even partial improvement and often there will be some residual impairment, either a motor weakness or a sensory numbness or both. Recovery is slower in the feet and legs than in the hands and arms.

There is no specific treatment that enhances nerve recovery. There are no drugs that will directly stimulate nerve regeneration or recovery. If you have severe and prolonged pain, then the pain may require narcotics often combined with antidepressants. In some cases, certain types of anticonvulsants would be helpful. Treatment options are subjects that you should discuss with your doctor, so you have accurate expectations of potential benefits and 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.

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