Radiation therapy is effective in many cases of primary brain tumors as well as in patients with metastatic tumors originating in the lung and breast. From 4,500 to 8,000 rads are delivered from “ports” on opposite sides of the skull directed at the tumor and suspicious areas by computerized methods. In most institutions this radiation dose is administered over a fifteen-to-thirty-day period, on an outpatient basis when possible. The benefits from radiation therapy are concentrated in the first year with about 70 percent achieving relief of symptoms and an improved quality of life, even though survival may not be prolonged.
During radiation therapy there may be loss of hair, fatigue, and other relatively minor although personally distressing complications.
The major complications of radiation therapy to the brain usually appear eighteen to twenty-four months after a total dosage of 6,000 rads or more. The radiation may damage brain cells and arteries, causing the formation of diffuse scar tissue. The consequences depend upon the areas of the brain irradiated. Paralysis or movement problems may develop if the spinal cord or the movement centers in the brain are irradiated. Intellectual decline may occur if the cerebral hemispheres are diffusely exposed. The prolonged survival of brain tumor patients has increased the incidence of radiation complications. Nevertheless, the benefit far outweighs the risk. There is little in the way of alternatives. Slow neutron and alpha particle rays, which have little effect on most brain tumors, have been used with considerable success in benign pituitary tumors without producing diffuse radiation damage, perhaps because of precise targeting.
Chemotherapy has been of small benefit to brain tumor patients. Many of the anticancer drugs do not cross the blood-brain barrier in sufficient amounts to destroy cancer cells. Injection of anticancer drugs directly into the spinal fluid, occasionally by utilizing an implanted reservoir mechanism, may be used in academic institutions.
Chemotherapy following surgery and radiation therapy has prolonged survival in some studies, but the true benefit does not seem to be substantial. Chemotherapy is largely ineffective against most metastatic brain tumors, with the possible exception of those arising from testicular cancer. Spread of a metastatic tumor over the surface of the brain and its linings, meningeal carcinomatosis, has been treated with some success by a combination of radiation therapy and chemotherapy. The anticancer drugs used most often in brain cancer are BCNU (carmustine), metho-trexate, hydroxyurea, and procarbazine.
There are, however, a number of other drugs that are important in the overall treatment of brain cancer. Both corticosteroids and anticonvul-sant drugs play a central role. Steroids may be given to rapidly reduce the swelling and buildup of fluid surrounding both primary and metastatic brain tumors. The benefit from the reduction of the mass effect generally, as well as the improvement in function, can be striking. It is often seen within twelve to twenty-four hours and may return speech, thought processes, and movement to normal, at least temporarily. Since tumor growth is not slowed by steroids, the symptoms may reappear as the growth increases. But even partial relief can be significant. Care should be taken to avoid sudden withdrawal of the steroids, since this can cause a rapid return of edema. Intracranial pressure mounts and symptoms quickly return, often with evidence of dangerous shifts.
Steroids also may be given to suppress brain swelling after surgery and radiation. They are also effective in giving the neurologist and neurosur-geon time to plan therapy without the immediate need to surgically reduce the pressure within the cranial cavity. Although steroids have a number of serious side effects, such as thinning of the bones, increased susceptibility to infections, mental changes and others, the benefits outweigh the complications when dealing with brain cancer.
Depending on the tumor’s specific type and location, between 20 and 70 percent of brain tumor patients will have seizures at some point. The seizures are usually the grand mal type, which begin in one place and spread quickly to involve the entire body. Even if a patient has not had a seizure, Dilantin or phenobarbital, the two most commonly used anticon-vulsant drugs, are given routinely on a preventive basis. They control the seizure problem almost without side effects. Stopping or reducing the dosage of anticonvulsant medication is not advised, since this can precipitate the very problem the drugs prevent.