Representative FLT-PET/CT and FDG-PET/CT images at baseline and during the third week of PD0332991 in responding and progressing patients. (A) Images from patient 3, who went on to achieve complete response, demonstrating substantial improvements in FLT uptake and more modest changes in FDG uptake. (B) Images from patient 12, whose best response was disease progression, demonstrating interval increases in the number of lesions and in tracer uptake on both sets of scans.