Fig. 1

Baseline and Follow-up MRI Scans of a Patient with Different Response Assessments

A. Baseline scan (a, b) shows a target lesion of 13 mm. First follow-up scan at week 8 (c, d) shows that the target lesion has decreased in size from 13 mm to 5 mm, and that a new lesion of 6 mm has appeared. Since a new lesion has developed, progressive disease (PD) is defined by mRECIST. However, according to the RANO-BM and iRANO-BM criteria, the diameter of the new lesion is added to the sum of the longest diameter (SLD), which makes the SLD 11 mm for the follow-up scan. Therefore, the response assessment would be stable disease (SD) by RANO-BM and iRANO-BM. B. Baseline scan (a, b) shows two target lesions with sizes of 13 and 8 mm. On the first follow-up scan at week 20 (c, d), the size of each target lesion has increased, and the response assessment would be progressive disease (PD) by mRECIST and RANO-BM. However, this MRI was taken within 6 months of immunotherapy-treatment initiation, and follow-up imaging after 3 months is required for iRANO-BM assessment. In the follow-up MRI at week 40 (e, f), the size of the target lesions has decreased, and this patient is diagnosed with stable disease (SD) by iRANO-BM