Background

The promise of Alzheimer’s disease (AD) biomarkers has led to their incorporation in new diagnostic criteria and in therapeutic trials; however, significant barriers exist to widespread use. Chief among these is the lack of internationally accepted standards for quantitative metrics. Hippocampal volumetry is the most widely studied quantitative magnetic resonance imaging (MRI) measure in AD and thus represents the most rational target for an initial effort at standardization.

Methods and Results

The authors of this position paper propose a path toward this goal. The steps include: 1) Establish and empower an oversight board to manage and assess the effort, 2) Adopt the standardized definition of anatomic hippocampal boundaries on MRI arising from the EADC-ADNI hippocampal harmonization effort as a Reference Standard, 3) Establish a scientifically appropriate, publicly available Reference Standard Dataset based on manual delineation of the hippocampus in an appropriate sample of subjects (ADNI), and 4) Define minimum technical and prognostic performance metrics for validation of new measurement techniques using the Reference Standard Dataset as a benchmark.

Conclusions

Although manual delineation of the hippocampus is the best available reference standard, practical application of hippocampal volumetry will require automated methods. Our intent is to establish a mechanism for credentialing automated software applications to achieve internationally recognized accuracy and prognostic performance standards that lead to the systematic evaluation and then widespread acceptance and use of hippocampal volumetry. The standardization and assay validation process outlined for hippocampal volumetry is envisioned as a template that could be applied to other imaging biomarkers.

Patient-reported outcome (PRO) measures are used to evaluate disease and treatments in many therapeutic areas, capturing relevant aspects of the disorder not obtainable through clinician or informant report, including those for which patients may have a greater level of awareness than those around them. Using PRO measures in mild cognitive impairment (MCI) and prodromal Alzheimer's disease (AD) presents challenges given the presence of cognitive impairment and loss of insight. This overview presents issues relevant to the value of patient report with emphasis on the role of insight. Complex activities of daily living functioning and executive functioning emerge as areas of particular promise for obtaining patient self-report. The full promise of patient self-report has yet to be realized in MCI and prodromal AD, however, in part because of lack of PRO measures developed specifically for mild disease, limited use of best practices in new measure development, and limited attention to psychometric evaluation. Resolving different diagnostic definitions and improving clinical understanding of MCI and prodromal AD will also be critical to the development and use of PRO measures.

Purpose

Oral temozolomide is approved in many countries for malignant glioma and for melanoma in some countries outside the USA. This study evaluated the exposure equivalence and safety of temozolomide by intravenous infusion and oral administration.

Methods

Subjects with primary central nervous system malignancies (excluding central nervous system lymphoma) received 200 mg/m2 of oral temozolomide on days 1, 2 and 5. On days 3 and 4, subjects received 150 mg/m2 temozolomide either as a 90-min intravenous infusion on one day or by oral administration on an alternate day.

Results

Ratio of log-transformed means (intravenous:oral) of area under the concentration–time curve and maximum concentration of drug after dosing for temozolomide and 5-(3-methyltriazen-1-yl)imidazole-4-carboxamide (MTIC) met exposure equivalence criteria (90% confidence interval = 0.8–1.25). Treatment-emergent adverse events were consistent with those reported previously in subjects with recurrent glioma treated with oral temozolomide, except for mostly mild and transient injection site reactions with intravenous administration.

Conclusions

This study demonstrated an exposure equivalence of a 90-min intravenous infusion of temozolomide and an equivalent oral dose.