My dad who is 74 years old was diagnosed with stage IV small cell lung cancer. He was supposed to start chemo next week, but they called and cancelled it saying they wanted to do an MRI of his brain and a PET scan of his body (i guess). He has a grapefruit sized tumor in his shoulder and a baseball sized tumor in his lung. The only thing they did between seeing the doctor and him saying chem for next week was a blood test. Does anyone know any reason why a blood test could change the schedule of what the oncologist originally wanted to do?