Primary Cns Lymphoma Review Article Text

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Primary central nervous system cns lymphoma is a non hodgkin's lymphoma that arises within and is restricted to the nervous system. It usually presents as a brain tumor, but may also involve the leptomeninges, eyes, spinal cord, or any combination of these sites 1. Formerly, the disease was rare, representing less than 1% of all intracranial tumors, but since 1974 there has been at least a threefold rise in incidence in apparently immunocompetent patients. It has also been recognized for decades that primary cns lymphoma occurs with increased frequency in patients with congenital eg, ataxia telangiectasia or acquired eg, renal transplant recipients immunodeficiencies. It is now most common in patients with the acquired immunodeficiency syndrome aids , as many as 6% of whom develop primary cns lymphoma during their illness.

It is so characteristic of the immunosuppression associated with aids that it is classified as an aids defining illness in hiv infected individuals. Historically, treatment of primary cns lymphoma was surgery followed by cranial irradiation the median survival was 12 to 18 months, and the 5 year survival rate, 3% to 4% in immunocompetent patients immunosuppressed individuals fared worse. Survival figures with this treatment approach were consistent in numerous retrospective series evaluating small numbers of patients 20 to 30 collected over several decades. These studies also demonstrated the aggressive biologic behavior of primary cns lymphoma, with untreated patients surviving only a few months. Furthermore, the collected series suggested that surgical resection had no significant therapeutic role in the treatment of this disease, because survival was not worsened if only biopsy for tissue diagnosis was performed.

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Because the disease was so infrequent, pursuit of more effective therapy seemed neither practical nor necessary. In the early 1980s, physicians began to see a rising number of immunocompetent patients with primary cns lymphoma, an increase later confirmed by epidemiologic data. During this time, the full force of the aids epidemic led to increased cases of aids related primary cns lymphoma, and recent studies demonstrate that the incidence continues to rise, as hiv infected individuals survive longer 2,3. These factors clearly highlighted the inadequacy of then current therapy, and clinical trials were begun in an effort to improve treatment. To design an appropriate therapeutic approach, a number of issues concerning the biologic behavior of primary cns lymphoma needed to be defined and incorporated into the treatment plan. Using the clinical staging criteria applied to systemic non hodgkin's lymphoma, primary cns lymphoma is a stage ie lymphoma that is, it involves a single extranodal site, the brain. Most patients with systemic stage ie non hodgkin's lymphoma can be treated effectively with involved field irradiation.

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Focal radiotherapy achieves a complete response rate of almost 100% and can yield 10 year survival or cure rates of 70% in patients with stage i disease 4. Using involved field radiotherapy whole brain radiotherapy for the treatment of primary cns lymphoma does not produce comparable control of disease. Two possible reasons are that 1 disease exists outside the radiotherapy field and that 2 pathologically, primary cns lymphoma has more aggressive biology than identical systemic lymphomas. The issue of dissemination of disease is more easily addressed than the question of a fundamental biologic difference between primary cns lymphoma and systemic lymphomas, but systemic and nervous system dissemination must be considered independently.

systemic dissemination not a factor

it has been hypothesized that an occult systemic lymphoma is the origin of primary cms lymphoma, because the nervous system has no lymph nodes or lymphatics, and thus the source of malignant lymphocytes in the cns must be from outside. If an occult systemic lymphoma accounts for disease in the nervous system, then primary cns lymph oma would simply be a stage iv lymphoma with an unusual and rare pattern of metastasis to cns only.

First, when systemic lymphoma spreads to the nervous system, it spreads to meninges and affects the brain in only 1% of patients 5. In those few patients with brain metastases, the lesions appear late in the course of their illness and are associated with recurrent or uncontrolled systemic disease, often specifically with bone marrow infiltration or retroperitoneal adenopathy. Second, patients with primary cns lymphoma have no evidence of systemic lymphoma, either at diagnosis or at autopsy.

At memorial sloan kettering cancer center, more than 100 non aids patients with primary cns lymphoma had a complete systemic evaluation at diagnosis, including body computed tomography ct scans, bone marrow aspiration, and biopsy, and not one had evidence of systemic lymphoma. There are two case reports of patients who presented with apparent primary cns lymphoma and had systemic lymphoma on evaluation, but one patient had two histologically different lymphomas, and the disease in the second patient likely represented systemic metastases from untreated primary cns lymphoma 6,7. Autopsy studies have found systemic lymphoma in only 7% to 8% of primary cns lymphoma patients, and most of these patients have a single site of microscopic disease believed to be a metastasis from their uncontrolled cns tumor. Rare patients with primary cns lymphoma develop clinically obvious systemic lymphoma, which may even develop in the context of undetectable cerebral tumor. In some of these patients, the systemic lymphoma may be a second primary, as primary cns lymphoma is seen occasionally in patients with a variety of prior systemic neoplasms 8 however, the development of systemic lymphoma is very unusual and does not represent the typical clinical behavior of primary cns lymphoma.

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