Cerebral Metastases

CEREBRAL METASTASES

A significant number of patients with cancer experience neuro-logic deficits caused by metastasis to the brain. Metastatic lesions to the brain constitute the most common neurologic complica-tion, occurring in 20% to 30% of patients with cancer (Nevidjon Sowers, 2000). This becomes important clinically as more pa-tients with all forms of cancer live longer as a result of improved therapies. Neurologic signs and symptoms include headache, gait disturbances, visual impairment, personality changes, altered mentation (memory loss and confusion), focal weakness, paralysis, aphasia, and seizures. These signs and symptoms can be devas-tating to both patient and family.

Medical Management

The treatment of metastatic brain cancer is palliative and involves eliminating or reducing serious symptoms. Even when palliation is the goal, distressing signs and symptoms can be relieved, thereby improving the quality of life for both the patient and family. Pa-tients with intracerebral metastases who are not treated have a steady downhill course with a limited survival time, whereas those who are treated may survive for slightly longer periods. The me-dian survival for patients with no treatment for brain metastases is 1 month; with corticosteroid treatment alone it is 2 months; radiation therapy extends the median survival to 3 to 6 months (Nevidjon & Sowers, 2000).

The therapeutic approach includes radiation therapy (the foundation of treatment), surgery (usually for a single intracranial metastasis), and chemotherapy; more often some combination of these treatments is the optimal method. Gamma knife radio-surgery is considered when three or fewer lesions are present.

PHARMACOLOGIC THERAPY

Corticosteroids are useful in relieving headache and alterations in level of consciousness. It is thought that corticosteroids (dexa-methasone, prednisone) reduce inflammation around the metasta-tic deposits and decrease the edema surrounding them. Other medications used include osmotic agents (mannitol, glycerol) to decrease the fluid content of the brain, which leads to a decreasein ICP. Antiseizure agents (eg, phenytoin) are used to prevent and treat seizures (Nevidjon & Sowers, 2000). Venous throm-boembolic events, such as deep vein thrombosis (DVT) and pul-monary embolism (PE), occur in about 15% of patients and are associated with significant morbidity. Anticoagulants are gener-ally not prescribed because of the risk for CNS hemorrhage; how-ever, prophylactic therapy with low-molecular-weight heparin is under investigation.

Chemotherapy plays a small role in managing brain metastasis as a result of poor penetration across the blood–brain barrier. Poor drug penetration and sensitivity of brain cells are two factors that determine the responsiveness of metastatic brain tumors to chemotherapy. Research is being directed at multidrug regimens and drug resistance (American Cancer Society, 2001). Encourag-ing results have been seen with chemotherapeutic agents such as carmustine (BCNU), lomustine (CCNU), and PCV (a triple-drug combination of procarbazine hydrochloride, lomustine, and vincristine). Promising results have been seen with the use of topotecan (Hycamtin), another chemotherapy agent.

Pain is managed in a stepladder progression in the doses and type of analgesic agents needed for relief. If the patient has severe pain, morphine can be infused into the epidural or subarachnoid space through a spinal needle and a catheter as near as possible to the spinal segment where the pain is projected. Small doses of morphine are administered at prescribed intervals.