Response assessment in neuro-oncology brain metastases (RANO-BM) criteria are recommendations for standardized tumor response and progression assessment in clinical trials involving brain metastases. Published in 2015, these should not be confused with the RANO criteria for high-grade glioma from the same group.
The RANO-BM criteria, similar to other systems, divides response into four types of response based on imaging (MRI or CT) and clinical features 1:
- complete response
- partial response
- stable disease
- progression
Technique
Gadolinium-enhanced MRI is the preferred imaging technique, while CT with and without contrast could be considered in resource-limited settings or patients with contraindications to MRI. Slice thickness is preferably 5 mm or less with 0 mm skip, and ideally ≤1.5 mm thickness with 0 mm skip.
Measurement is based on unidimensional longest diameter. Measurements are recorded in metric notation.
Measurable disease is defined as a contrast-enhancing lesion that is at least 10 mm in longest diameter, visible on two or more axial slices, and at least 5 mm in diameter perpendicular to the longest diameter. Non-measurable disease includes lesions that are less than 10 mm, those with borders that are not able to be reproducibly measured, dural metastases, bony metastases, leptomeningeal metastases, and cystic-only lesions.
At the baseline assessment, performed close to the treatment start and no more than 4 weeks beforehand, up to 5 target lesions are identified based on size and those that can be measured reproducibly. All other CNS lesions are non-target lesions and should be reported but not necessarily measured.
A sum of the longest diameters for all target lesions is the main measure for overall tumor response assessment, in composite with a qualitative assessment of non-target lesions, as part of the following criteria.
Criteria
Complete response
All of the following criteria are required for complete response:
- imaging features
- target lesions: none
- non-target lesions: none
- new lesions: none
- clinical features
- corticosteroids: none
- clinical status: stable or improved
Partial response
All of the following criteria are required for partial response:
- imaging features
- target lesions: ≥30% decrease in sum longest distance relative to baseline
- non-target lesions: stable or improved
- new lesions: none
- clinical features
- corticosteroids: stable or decreased
- clinical status: stable or improved
Stable disease
All of the following criteria are required for stable disease:
- imaging features
- target lesions: <30% decrease relative to baseline but <20% increase in sum longest distance relative to nadir
- non-target lesions: stable or improved
- new lesions: none
- clinical features
- corticosteroids: stable or decreased
- clinical status: stable or improved
Progressive disease
Any of the following criteria can indicate progressive disease:
- imaging features
- target lesions: ≥20% increase in sum longest distance relative to nadir
- non-target lesions: unequivocal progression of existing enhancing or tumor-related non-enhancing (T2/FLAIR) lesions
- new lesions: present*
- clinical features
- clinical status: worse
*In patients receiving immunotherapy, new lesions alone cannot constitute progressive disease.
In patients who received stereotactic radiosurgery, clinical evidence of progression and radiologic evidence may conflict, which may require follow-up or more advanced imaging to clarify.