Evaluation of FLT-PET-CT as an imaging biomarker of proliferation in primary breast cancer

BACKGROUND: [(18)F]fluorothymidine (FLT) has been proposed as a positron emission tomography (PET)-imaging biomarker of proliferation for breast cancer. The aim of this prospective study was to assess the feasibility of FLT-PET-CT as a technique for predicting the response to neoadjuvant chemotherapy (NAC) in primary breast cancer and to compare baseline FLT with Ki-67. METHODS: Twenty women with primary breast cancer had a baseline FLT-PET-CT scan that was repeated before the second cycle of chemotherapy. Expression of Ki-67 in the diagnostic biopsy was quantified. From the FLT-PET-CT scans lesion maximum and mean standardised uptake values (SUV(max), SUV(mean)) were calculated. RESULTS: Mean baseline SUV(max) was 7.3, and 4.62 post one cycle of NAC, representing a drop of 2.68 (36.3%). There was no significant association between baseline, post chemotherapy, or change in SUV(max) and pathological response to NAC. There was a significant correlation between pre-chemotherapy Ki-67 and SUV(max) of 0.604 (P=0.006). CONCLUSIONS: Baseline SUV(max) measurements of FLT-PET-CT were significantly related to Ki-67 suggesting that it is a proliferation biomarker. However, in this series neither the baseline value nor the change in SUV(max) after one cycle of NAC were able to predict response as most patients had a sizeable SUV(max) reduction.