Monoclonal antibody therapy for central nervous system lymphomas: an emerging treatment paradigm

Primary central nervous system post-transplant lymphoproliferative disorders following allogeneic hematopoietic stem cell transplantation

Post-transplant lymphoproliferative disorder (PTLD) is a serious complication after allogeneic hematopoietic stem cell transplantation (HSCT). Extra nodal involvement is common in PTLD, but isolated involvement of the central nervous system (CNS) is extremely rare. Given the rarity of primary CNS-PTLD there is no consensus on optimal treatment. We report a patient who developed Epstein-Barr virus related primary CNS-PTLD following allogeneic HSCT who was treated with the monoclonal anti-CD20 antibody rituximab and reduction of immunosuppression. In addition, we review the literature and discuss treatment options for patients with primary CNS-PTLD following allogeneic HSCT.

Primary CNS lymphoma

Primary CNS Lymphoma (PCNSL) accounts for 3% of all primary brain tumors with a median age at onset of about 62 years. In the vast majority of cases, PCNSL presents as unifocal or multifocal enhancing lesions on MRI, frequently adjacent to the ventricles. Stereotactic biopsy is the diagnostic procedure of choice revealing high-grade malignant non-Hodgkin's B-cell lymphoma in more than 90% of cases. Therapy is not evidence based. When eligible, patients should be included in clinical trials. In patients younger than 60 years cure is the aim. Polychemotherapy based on high-dose methotrexate (MTX) or alternatively high-dose chemotherapy with autologous stem cell rescue should be offered to patients eligible for this regimens. For patients over 60 years of age no curative regimen with acceptable toxicity has yet been established. An MTX-based chemotherapy, for example, in combination with temozolomide, is recommended. The role of radiotherapy as part of the initial treatment is not established; however, the combination of radiotherapy with MTX-based chemotherapy potentially leads to severe long-term neurotoxic sequelae. Therefore, radiotherapy as part of the initial therapy is not recommended by the author outside clinical trials. At relapse or in cases of refractory disease, patients will frequently benefit of salvage therapy, which depends on the initial treatment.

Primary central nervous system lymphoma

There is no class I evidence for any therapeutic option in primary central nervous system lymphoma (PCNSL). When possible, patients should be included in clinical trials. The role of surgery is restricted to stereotactic biopsy in order to gain material for histopathologic diagnosis. Radiotherapy alone is associated with a median survival of no more than 1.5 years; cure is exceptional. However, in patients aged younger than 60 years, cure is the therapeutic aim. Polychemotherapy based on high-dose methotrexate with deferred radiation results in long-term survival in most of these patients and possibly cure in a substantial fraction of these patients. With regard to chemotherapy in PCNSL, the following must be considered: 1) the most efficient drug in PCNSL is methotrexate at a dosage of at least 1.5 g/m(2) per single dose; 2) methotrexate alone will lead to complete remission in only some patients, whereas the combination of methotrexate with other drugs is more efficient; and 3) the value of additional intraventricular chemotherapy and the necessity of "consolidation" radiotherapy after response to chemotherapy are not yet defined. For patients aged older than 60 years, no curative regimen with acceptable toxicity has yet been established. The combination of radiotherapy with methotrexate-based chemotherapy leads to severe long-term neurotoxic sequelae, ie, cognitive dysfunction, in most older patients and in some patients aged younger than 60 years.

Stratified phase II trial of cetuximab in patients with recurrent high-grade glioma

BACKGROUND

To evaluate the antitumor activity and toxicity of single-agent cetuximab in patients with recurrent high-grade glioma (HGG) after failure of surgery, radiation therapy, and chemotherapy.

PATIENTS AND METHODS

In this two-arm, open-label, phase II study patients were stratified according to their epidermal growth factor receptor (EGFR) gene amplification status. Cetuximab was administered intravenously at a dose of 400 mg/m(2) on week 1 followed by weekly dose of 250 mg/m(2). The primary end point for this study was the response rate in both study arms separately.

RESULTS

Fifty-five eligible patients (28 with and 27 without EGFR amplification) tolerated cetuximab well. Three patients (5.5%) had a partial response and 16 patients (29.6%) had stable disease. The median time to progression was 1.9 months [95% confidence interval (CI) 1.6-2.2 months]. Whereas the progression-free survival (PFS) was <6 months in the majority (n = 50/55) of patients, five patients (9.2%) had a PFS on cetuximab of >9 months. Median overall survival was 5.0 months (95% CI 4.2-5.9 months). No significant correlation was found between response, survival and EGFR amplification.

CONCLUSIONS

Cetuximab was well tolerated but had limited activity in this patient population with progressive HGG. A minority of patients may derive a more durable benefit but were not prospectively identified by EGFR gene copy number.