Also, sensitivity of FDG-PET and PET/CT improved in patients with shorter tumor markers (calcitonin and CEA) doubling times [6, 10, 14, 16, 18], confirming the usefulness of these imaging methods in patients with more aggressive disease (with high glucose consumption and high FDG uptake) compared to those with slowly progressive disease (with low glucose consumption and low FDG uptake) [40]. This evidence concerns the gene CALCA and neoplasm.