Comparison of (18)F-fluorothymidine Positron Emission Tomography/Computed Tomography and (18)F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Patients with Breast Cancer

The uptake of (18)F-fluorothymidine ((18)F-FLT) depends on cells’ proliferative rates. We compared the characteristics of (18)F-FLT positron emission tomography/computed tomography (PET/CT) with those of (18)F-fluorodeoxyglucose ((18)F-FDG) PET/CT for breast cancer. We prospectively diagnosed patients with breast cancer who underwent (18)F-FLT PET/CT and (18)F-FDG PET/CT. Subsequently, significant differences and correlation coefficients of the maximum standardized uptake value (SUVmax) in primary breast cancer and axillary lymph nodes were statistically evaluated. We enrolled eight patients with breast cancer. In six treatment-naive patients, the SUVmax for primary lesions showed a significant difference (mean, 2.1 vs. 4.1, p = 0.031) and a strong correlation (r = 0.969) between (18)F-FLT and (18)F-FDG. Further, although the SUVmax for the axillary lymph nodes did not show a significant difference between (18)F-FLT and (18)F-FDG (P = 0.246), there was a strong correlation between the two (r = 0.999). In a patient-by-patient study, there were cases in which only (18)F-FDG uptake was observed in lymph nodes and normal breasts. Bone metastases demonstrated lower accumulation than bone marrow on the (18)F-FLT PET/CT. In conclusion, a strong correlation was observed between the (18)F-FLT PET/CT and (18)F-FDG PET/CT uptake. Differences in the biochemical characteristics of (18)F-FLT and (18)F-FDG were reflected in the accumulation differences for breast cancer, metastatic lesions, and normal organs.