The diagnosis of primary CNS lymphoma should be based on biopsy of the lesion if possible. If the situation precludes biopsy and the diagnosis appears probable, evaluation and management should be discussed and planned with a medical oncology member of the Lymphoma Tumour Group at a BCCA Centre. All patients with primary lymphoma of the CNS should have HIV antibody testing and a detailed ophthalmologic evaluation. Bone marrow biopsy and abdominopelvic CT scanning are not necessary in these patients. Treatment of patients with primary CNS lymphoma is based on neurologic and performance status after initial treatment with pharmacologic doses of corticosteroids (dexamethasone 8 to 16 mg orally each day). Patients who remain very frail or moribund, or continue to experience severe dementia, despite corticosteroids should not have their lymphoma further actively treated and care should concentrate on symptomatic palliation. All others should be offered treatment with high dose methotrexate (LY HD MTX) with leucovorin rescue. If renal dysfunction precludes high dose methotrexate, or if the patient is deemed not a candidate for high dose methotrexate for other reasons, whole brain plus posterior globe irradiation should be considered.

Lymphomatous involvement of the leptomeninges can occur due to spread from systemic or primary parenchymal CNS lymphoma. Diagnosis is based on CSF cytology and typical cranial and peripheral nerve abnormalities. Leptomeningeal lymphoma is very difficult to eradicate and reliable treatment has not been defined. High dose systemic methotrexate has been shown to provide superior palliation compared to intrathecal or intraventricular chemotherapy (Glantz, J Clin Oncol, 1998; 16: 1561-7). Patients with leptomeningeal lymphoma and adequate renal function (creatinine clearance >60ml/min) should be given high dose methotrexate with leucovorin rescue (LY HD MTX). Otherwise systemic high dose corticosteroids offer the best palliation.

Patients considered to have a high risk of parenchymal CNS relapse (such as patients with primary testicular lymphoma, patients with advanced stage aggressive B-cell lymphoma and renal/adrenal involvement, or patients with multiple high risk features for CNS relapse) should be considered for the addition of moderate dose methotrexate (3.5 g/m²) in between doses of standard systemic chemotherapy. Management in this situation should be discussed and planned with a medical oncology member of the Lymphoma Tumour Group at a BCCA Centre. LYCHOPRMTX Protocol (01 Mar 2022)