FDG-PET in monitoring therapy of breast cancer

Abstract

Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET) has been used successfully for the staging and re-staging of breast cancer. Another significant indication is the evaluation of therapy response. There are only few data on FDGPET in breast cancer after radiation therapy. The same holds true for chemotherapy. Only the therapy response in locally advanced breast cancer after chemotherapy has been investigated thoroughly. Histopathologic response could be predicted with an accuracy of 88-91% after the first and second course of therapy. A quantitative evaluation is of course a prerequisite when FDG-PET is used for therapy monitoring. Only few studies have focussed on hormone therapy. Here, a flare phenomenon with increasing SUVs after initiation of tamoxifen therapy has been observed. More prospective multicenter trials will be needed to make FDG-PET a powerful tool in monitoring chemotherapy in breast cancer. Whole body imaging with fluorine-18 deoxyglucose PET (FDG-PET) has gained widespread acceptance for the staging and restaging of breast cancer (Biersack et at. 2001; Kostakoglu and Goldsmith 2003; Grahek et al. 2004). Another significant indication for FDG-PET is the evaluation of therapy response. Above that the proof of viability of tumour tissue after termination of chemotherapy is another indication for PET. The evaluation of therapy response is usually done by CT, sonography or MRI (Biersack and Palmedo 2003). These imaging procedures allow the detection of changes of the tumour size or volume. Because the majority of cells within a tumour mass are in a resting state, reduction of tumour volume requires time and might be masked by unspecific effects (edema as a result of necrosis). In contrast, cellular uptake of FDG is a function of cell viability and seems to be associated with the increased cell turnover. Animal models have shown that, after therapy, the amount of tumour FDG uptake reflects the number of viable tumour cells present (Haberkorn et al. 1987). Already in 1989, Minn et al. (1989) studied patients with breast cancer before and after therapy using FDG-PET. Even using a planar gamma camera equipped with thick lead collimators, they could show that increasing FDG uptake over time was associated with tumour progression. These data make evident that new cumbersome sophisticated FDG imaging procedures may further increase the diagnostic significance of FDG-PET in therapy monitoring. © 2008 Springer-Verlag Berlin Heidelberg.