With a CT or bone scan, how is arthritic activity differentiated between bone metastasis? Is it an art vs a science? I was diagnosed stage 3 with a large tumor back in March of 2002. I am 42 years old. I have recently developed severe back pain - sciatic nerve involvement. Scans show no cancer in lumbar area, but pain continues - is at it's worst when sitting or lying down. Pain diminishes the more I move! I don't recall exact terminology, but scan reports indicate activity consistent with arthritic activity, degenerative disk disease. I am treating with anti-inflammatory and physical therapy, but don't notice much if any improvement. Would an MRI or PET scan be warranted at this time? I am trying to decide how concerned I should be. I know I am at hight risk for recurrence. Thank you for any advice you can provide.