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

Background:

¹⁸F]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.