Primary central nervous system lymphoma: a review

Early complete response during chemotherapy predicts favorable outcome in patients with primary CNS lymphoma

In primary central nervous system lymphoma (PCNSL), 2 international prognostic scores have been developed to estimate the outcome according to certain "prognostic groups". However, these scores do not predict the individual course of a single patient under therapy. In this analysis, we addressed the question of whether early tumor remission in patients still under therapy, according to magnetic resonance imaging (MRI) criteria, helps to predict long-term outcome. Eighty-eight patients treated with 6 polychemotherapy cycles within a pilot/phase II trial underwent MRI scanning within 72 hours prior to initiation of therapy, after the second chemotherapy cycle, and after completion of chemotherapy. Response was assessed by contrast-enhanced MRI of the brain according to the Macdonald criteria. Median follow-up was 42 months (range, 0-124 months). Patients achieving a complete radiographic response after 2 courses of chemotherapy (n = 18) had a significantly longer median overall survival (OS) (not reached) and median time-to-treatment failure (TTF) (not reached) than patients with complete response (CR) after termination of treatment but with only a partial response after the second cycle (n = 24) (OS: 55 months; TTF: 32 months) (P < .01). Early complete tumor response assessed by MRI after the second of sixth scheduled chemotherapy cycles was highly predictive for both OS and TTF in patients with PCNSL treated in this series.

Imaging of central nervous system lymphomas with iodine-123 labeled rituximab

Most patients with primary central nervous system (CNS) lymphoma (PCNSL) relapse after initial response to chemotherapy or the combination of chemotherapy and irradiation. Thus, novel treatment regimens for relapsed PCNSL are needed. As the majority of PCNSL are B-cell neoplasms expressing the CD20 antigen, treatment with the chimeric monoclonal antibody (MAb) rituximab might be reasonable. Nevertheless, the potential efficacy of intravenous rituximab in PCNSL seems to be limited as MAbs are high molecular weight proteins, which might be unable to pass the blood brain barrier. Thus, we performed dosimetric measurements with iodine-123 (123I)-rituximab to evaluate rituximab uptake in PCNSL after systemic intravenous administration. We analyzed four patients with PCNSL receiving a preinfusion of 250 mg/m2 rituximab followed by 200-500 MBq of the gamma-emitter 123I-rituximab. Single photon emission computed tomography (SPECT) was performed 1, 24 and 48 h after administration of the radio-immunoconstruct. Only one patient showed a very weak or questionable uptake of 123I-rituximab into tumor tissue which was ninefold lower compared with the blood-pool accumulation. These data suggest that systemic MAb-based radio-immunotherapy is not feasible in patients with PCNSL because a sufficient activity in the tumor will be associated with severe hematotoxicity. If an uptake of therapeutic rituximab doses into PCNSL can be achieved remains questionable.

VH gene analysis of primary CNS lymphomas

Primary CNS lymphomas (PCNSL) are highly malignant non-Hodgkin's lymphomas of B cell origin associated with a poor prognosis. These neoplasms show variable sensitivity to radio- and chemotherapy. A molecular basis for these differences in treatment responses has not yet been established for primary CNS lymphomas in a comprehensive series of patients. Here, we performed PCR analyses of the immunoglobulin (Ig) gene rearrangements of 18 PCNSL, including nine patients who responded well to therapy and nine patients who showed resistance to treatment. Variable gene segment distribution, mutation frequency of variable region genes, and clinical course were analyzed. Our data suggest a tendency towards a higher mean mutation frequency (17.2%) in patients responding to treatment and a lower mutation frequency (11.8%) in patients exhibiting a poor response to therapy, respectively. Furthermore, a restricted usage of the VH4 gene family was observed in the majority of nonresponding patients. To further validate the prognostic impact of these molecular parameters, studies in a larger cohort of patients will be required.

Neuroradiological findings in primary cerebral lymphomas of non-AIDS patients

Primary central nervous system lymphomas (PCNSL's) are rare tumours which generally accounted for 1.0-1.5% of all intracranial neoplasms. However, within the last decade the frequency of cerebral lymphomas has dramatically increased. We retrospectively analysed the neuroradiological findings (computed tomography (CT), MRI, angiography) in 37 patients with PCNSL. Thirty patients with the clinically and neuroradiologically suspected diagnosis of cerebral lymphoma underwent CT- or MRI-guided stereotactic biopsy. In seven cases an open surgical intervention was performed. Preoperatively, CT with and without contrast medium was performed in all but two cases. Twenty-eight patients received MRI (axial SE T2 weighted, triplanar SE T1 weighted, triplanar SE T1+Gadolinium). Additionally, in 9 patients cerebral angiography was performed. Typical neuroradiological patterns are: (1) iso- or hyper-density (85.5%) on unenhanced CT scan with marked contrast enhancement (87.7%); (2) infiltration/contact of leptomeningeal and/or ependymal spaces (97.3%); (3) hyperintensity on T2 with moderate oedema (80.3%). Histopathological work-up included conventional and immunohistochemical stains performed on formalin fixed and paraffin embedded bioptical specimen. Despite widely used preoperative dexamethasone treatment, an accurate histopathological diagnosis of PCNSL of B cell type was established in all cases except one. The high percentage of accurate histopathological diagnosis was based on: (1) great mean sample volume per biopsy site; (2) great number of biopsies in patients suspected to have cerebral lymphomas; and (3) MR-guided stereotactic procedures if the lesion was not clearly identifiable on CT scan.