ImportanceMalignant primary brain tumors cause more than 15 000 deaths per year in the United States. The annual incidence of primary malignant brain tumors is approximately 7 per 100 000 individuals and increases with age. Five-year survival is approximately 36%.ObservationsApproximately 49% of malignant brain tumors are glioblastomas, and 30% are diffusely infiltrating lower-grade gliomas. Other malignant brain tumors include primary central nervous system (CNS) lymphoma (7%) and malignant forms of ependymomas (3%) and meningiomas (2%). Symptoms of malignant brain tumors include headache (50%), seizures (20%-50%), neurocognitive impairment (30%-40%), and focal neurologic deficits (10%-40%). Magnetic resonance imaging before and after a gadolinium-based contrast agent is the preferred imaging modality for evaluating brain tumors. Diagnosis requires tumor biopsy with consideration of histopathological and molecular characteristics. Treatment varies by tumor type and often includes a combination of surgery, chemotherapy, and radiation. For patients with glioblastoma, the combination of temozolomide with radiotherapy improved survival when compared with radiotherapy alone (2-year survival, 27.2% vs 10.9%; 5-year survival, 9.8% vs 1.9%; hazard ratio [HR], 0.6 [95% CI, 0.5-0.7]; P < .001). In patients with anaplastic oligodendroglial tumors with 1p/19q codeletion, probable 20-year overall survival following radiotherapy without vs with the combination of procarbazine, lomustine, and vincristine was 13.6% vs 37.1% (80 patients; HR, 0.60 [95% CI, 0.35-1.03]; P = .06) in the EORTC 26951 trial and 14.9% vs 37% in the RTOG 9402 trial (125 patients; HR, 0.61 [95% CI, 0.40-0.94]; P = .02). Treatment of primary CNS lymphoma includes high-dose methotrexate-containing regimens, followed by consolidation therapy with myeloablative chemotherapy and autologous stem cell rescue, nonmyeloablative chemotherapy regimens, or whole brain radiation.Conclusions and RelevanceThe incidence of primary malignant brain tumors is approximately 7 per 100 000 individuals, and approximately 49% of primary malignant brain tumors are glioblastomas. Most patients die from progressive disease. First-line therapy for glioblastoma is surgery followed by radiation and the alkylating chemotherapeutic agent temozolomide.

Primary central nervous system lymphoma (PCNSL) is a rare and aggressive non-Hodgkin lymphoma that affects the brain, eyes, cerebrospinal fluid (CSF), or spinal cord without systemic involvement. Here, we review the clinical presentation, diagnostic work-up, novel pathophysiologic insights, and treatment of immunocompetent PCNSL patients. Diagnosis of PCNSL requires a high level of suspicion as clinical signs and deficits can vary depending upon the involved CNS compartments. Rapid initiation of therapy is essential for good neurologic recovery and disease control. In general, the prognosis of PCNSL has improved significantly over the past few decades, largely due to the introduction and wide-spread use of high-dose methotrexate (MTX) chemotherapy, considered the backbone of first-line polychemotherapy treatment. Upon completion of MTX-based treatment, a consolidation strategy is often required and can consist of non-myeloablative or myeloablative chemotherapy followed by autologous stem cell transplant, radiation, maintenance therapy, or observation. Unfortunately, relapse is common and 5-year survival rates stand at only 30-40%. Novel insights into the pathophysiology of PCNSL have identified key mechanisms in tumor pathogenesis including activation of the B-cell receptor pathway, a suppressed tumor immune microenvironment, and immune evasion. These insights have led to the identification of novel small molecules and agents targeting these aberrant pathways. Agents such as the Bruton Tyrosine Kinase (BTK) inhibitor ibrutinib or immunomodulatory drugs (IMiDs) like lenalidomide or pomalidomide have shown promising response rates in the clinical trial setting for recurrent/refractory PCNSL and are increasingly being adopted in clinical use.