Every 8 weeks. In the event of a PR or CR tumor imaging assessments may be performed every 3 months (+/ - 2 weeks) at the discretion of the investigator. Tumor assessment should be continued beyond end of treatment in participants who have not experienced PD until they experience PD in order to assess PFS. MRI will be used when CT scan is not an option to follow the disease clinically. Gadolinium will be used only for clinically indicated MRIs. Bone scans and other imaging assessments may also be performed as clinically indicated.