Effect of colony-stimulating factor on FDG uptake in bone marrow of patients with breast cancer

Objectives Colony-stimulating factor (CSF) may interfere with F-18 FDG PET/CT readings by increasing marrow activity. Unfortunately, however, it is not always possible to observe the recommended 3-week waiting period after discontinuation of CSF treatment before taking PET/CT. The purpose of this study is to determine whether a shorter interval (of 1 week) is acceptable for patients in such clinical situations.

Methods Twenty-one patients with locally advanced breast cancer underwent PET/CT before and after neoadjuvant chemotherapy with CSF. From each person’s spine, the maximum and average standardized uptake values for both time points (SUVmax1 and SUVmax2, SUVavg1 and SUVavg2) and the percent change between the two (Δ%SUVmax, Δ%SUVavg) were calculated. Visual analysis was based on a 3-point system. PET/CT results were correlated with days after CSF cessation: 0-7 days (n=14) or 8-31 days (n=7).

Results The SUVmax and SUVavg in the delayed PET/CT after discontinuation of CSF were as follows: 0-7 days, (2.5±0.5, 2.7±0.5); 8-31 days, (2.1±0.3, 2.2±0.3). Among patients with CSF treatment within 7 days prior to PET scanning, the difference between SUVmax1 and SUVmax2 (p<0.001) as well as that of SUVavg1 and SUVavg2 were statistically significant (p<0.001). However, in those who underwent scanning 8-31 days after CSF cessation, these were no longer statistically significant (p=0.497 and p=0.153, respectively). The remaining variables, including visual analysis, also only showed statistically significant changes when CSF was discontinued within 7 days prior to PET scanning.

Conclusions The difference between baseline and post-CSF treatment SUVs was statistically significant for up to 7 days after discontinuation, but not thereafter. In those patients in whom chemotherapy cycles warrant immediate evaluation of response, it may be acceptable to allow for a shorter minimum waiting period of 1 week between last CSF injection and follow-up PET/CT