Stable metabolic disease on FDG-PET provides information on response to endocrine therapy for breast cancer

The aim of this study was to assess whether outcome in advanced breast cancer patients is related to metabolic response to endocrine therapy determined by fluorodeoxyglucose positron-emission tomography (FDG-PET).

We retrospectively identified 21 consecutive breast cancer patients receiving endocrine therapy for metastatic disease (mean number of previous therapies 3.6±3.5). All patients had been evaluated with at least 2 FDG-PETs. The first scan was performed by initiation of endocrine therapy. The second scan was performed after a mean of 3.8±1.14 months. Seventy-two FDG-avid lesions were identified and followed. The mean change in SUVmax (ΔSUVmax) was calculated per patient.

ΔSUVmax dichotomized using the group median as cut-off (8.6%) was predictive of progression-free survival (PFS). The median PFS for the response-group (N.=10, median ΔSUVmax -20.9%) was 10.1 months. The median PFS for the progressive disease-group (N.=11, median ΔSUVmax 40.6%) was 6.7 months (log-rank testing P=0.033).

Our data suggest that breast cancer patients under hormonal therapy with stable disease on FDG-PET have a longer PFS when compared to non-responders. This finding is new, supporting the value of endocrine therapy among patients with advanced breast cancer.