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Natalizumab, a highly effective therapy for relapsing-remitting multiple sclerosis, is associated with a risk of progressive multifocal leukoencephalopathy (PML). The objective of this analysis was to examine factors predicting survival in a large natalizumab-associated PML global population. Patients with natalizumab-associated PML identified through postmarketing surveillance were followed up for up to 24 months using a structured questionnaire completed by treating physicians. Demographic and clinical characteristics, JC viral load, magnetic resonance imaging (MRI) results, and Expanded Disability Status Scale (EDSS) and Karnofsky Performance Scale (KPS) scores were compared in survivors and nonsurvivors. Kaplan-Meier analysis was used to model survival function. Among the 336 patients included in this analysis, 76 % survived, with mean follow-up time from PML diagnosis of 16.1 months for survivors; mean time from diagnosis to death was 4.7 months for nonsurvivors. Survivors were significantly younger at diagnosis, had significantly lower EDSS scores and higher KPS scores prior to PML diagnosis, and had significantly lower cerebrospinal fluid JC viral load at the time of diagnosis. Patients with less extensive disease on MRI at diagnosis had a higher survival rate than those with widespread disease. Survivors generally had less functional disability pre-PML, at PML diagnosis, and in subsequent months. In survivors, functional disability appeared to stabilize approximately 6 months post-PML diagnosis. In this analysis, younger age at diagnosis, less functional disability prior to PML diagnosis, lower JC viral load at diagnosis, and more localized brain involvement by MRI at the time of diagnosis appeared to predict improved survival in natalizumab-associated PML. [ABSTRACT FROM AUTHOR]

Objective As of 3 September 2013, 399 cases of natalizumab-associated progressive multifocal leukoencephalopathy ( PML) were confirmed in multiple sclerosis ( MS) patients. We evaluated outcomes of natalizumab-treated MS patients who were asymptomatic at PML diagnosis. Methods Analyses included data available as of 5 June 2013. Asymptomatic patients diagnosed with PML by magnetic resonance imaging ( MRI) findings and JC virus DNA detection in the central nervous system were compared with patients presenting with symptoms at diagnosis. Demographics, MRI, and survival over 12 months were analyzed. Expanded Disability Status Scale ( EDSS) and Karnofsky Performance Scale ( KPS) scores were recorded pre- PML, at diagnosis, and at 6 and 12 months post-diagnosis. Results A total of 372 PML cases were analyzed; 30 patients were asymptomatic and 342 were symptomatic at PML diagnosis. Classifications of PML lesions on MRI in asymptomatic versus symptomatic patients were unilobar in 68% versus 37%, multilobar in 21% versus 24%, and widespread in 11% versus 40%. In both groups with unilobar lesions, frontal lobe lesions predominated. Prior to PML, mean EDSS and KPS scores were similar for asymptomatic and symptomatic patients. At diagnosis, mean EDSS score was significantly lower for asymptomatic patients (4.1; n = 11) than for symptomatic patients (5.4; n = 193; P = 0.038). Six months after PML diagnosis, asymptomatic patients had less functional disability than symptomatic patients. As of 5 June 2013, 96.7% of asymptomatic patients and 75.4% of symptomatic patients were alive. Interpretation PML patients asymptomatic at diagnosis had better survival and less functional disability than those who were symptomatic at diagnosis. [ABSTRACT FROM AUTHOR]

Two letters to the editor are presented in response to the article "Natalizumab-Associated Progressive Multifocal Leukoencephalopathy" in the May 17, 2012 issue.