The RANO Criteria and Keeping Pace with Discovery

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LESION MEASUREMENT
Lesion measurement is often challenging when implementing the RANO criteria. This is due to the complex nature of different Brain tumors and, to some extent, a lack of specific instruction in the publication. It is important to ensure that a consistent imaging plane is used for measurement. Measurements should ideally be performed on the axial plane while other imaging planes are utilized to evaluate the extent of tumor and best slice for performing bi-dimensional measurements according to RANO.
Measuring across cystic and necrotic areas can also be a challenge. During the baseline evaluation, the neuroradiologists will typically measure the largest lesions whenever possible, using caution to ensure selected lesions will allow reproducible, repeated measurements, and to avoid measurement of tumor around a cyst or surgical cavity. While RANO suggests the cystic or surgical cavity should not be measured in determining response, it might be difficult to be excluded due to the brain tumor heterogeneity nature. As a general rule, if the cystic or necrotic area exceeds 25% of the entire tumor, it should not be included in the measurement.
At follow-up, the lesion should be measured in a similar method to baseline and, when possible, on a comparable slice, as well as utilizing the same area of measurement of the lesion. For example, if a lesion was measured at baseline and included part of the surgical cavity and/or cystic component, this same methodology should apply at follow-up. If the approach to measuring a lesion at follow-up varies significantly from the way it was measured at baseline, the measurements may not accurately reflect the tumor status at the given time point. It is thus essential to maintain a consistent methodology of assessing and evaluating the brain lesion from the baseline so that reproducible and accurate measurements can be used to evaluate tumor growth. The Figure below shows several axial slices of glioblastoma tumor at baseline and the complexity of selecting the best slice for measurement in a subject who had (partial) surgical tissue sampling.