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

BACKGROUND: 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). METHODS: 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. RESULTS: 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). CONCLUSIONS: 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.