40. AN UPDATE ON THE DEVELOPMENT OF A NEW TOOL TO ASSESS RESPONSE IN LEPTOMENINGEAL METASTASIS

In 2016, a standardized scorecard to aid in the evaluation of MRI findings during the course of disease was proposed by the RANO leptomeningeal metastasis (LM) subcommittee. In this scorecard, LM main features and the different CNS metastases types were to be reported as present or absent, dimensions of measurable nodules were to be noted, and changes from the previous MRI were to be scored from -3 to +3. A feasibility and validation study of this scorecard was performed by asking 19 experts to evaluate response in 22 patients diagnosed with and treated for LM. The outcome was disappointing in that the scorecard appeared to be too complicated (Le Rhun et al. Neuro-Oncology 2019;21:648–658). Specific challenges were (i) to understand that the form should be used to rate the current MRI and to compare it with the previous one, (ii) to use the proposed rating with “minus” or “plus” options to assess the change and (iii) to derive a sum score that does not take into consideration (per instruction) changes for the items “hydrocephalus”, “brain metastases” and “parenchymal medullary metastases”. In addition to the apparent challenges for experienced raters to use the LANO scorecard instructions without further instructions, we identified additional weaknesses. These include to eliminate epidural metastases from response assessment, to include the definition of a nodule, the distinction of leptomeningeal versus parenchymal brain disease, and to include parallel, but clearly separate criteria to document brain parenchymal disease. The revised, published proposal for a new scorecard has been used to rate another series of LM cases by experienced neuro-oncologists from March to May 2020. First analyses of this novel feasibility and validation study will be available in August.