- Measurable disease is defined as at least one lesion that can be accurately measured in at least one dimension (longest diameter to be recorded); each lesion must be greater than or equal to 10 mm when measured by computed tomography (CT), magnetic resonance imaging (MRI), or caliper measurement by clinical exam; or greater than or equal to 20 mm when measured by chest x-ray; lymph nodes must be greater than or equal to 15 mm in short axis when measured by CT or MRI