Assessment of response to endocrine therapy using FDG PET/CT in metastatic breast cancer: a pilot study

Purpose The purpose of this pilot study was to assess whether outcome in metastatic or recurrent breast cancer patients is related to metabolic response to endocrine therapy determined by F-18-FDG PET/CT. Methods The study group comprised 22 patients with breast cancer (age 58 +/- 11 years, mean +/- SD) who were scheduled to receive endocrine therapy. They were systematically assessed by PET/CT at baseline and after a mean of 10 +/- 4 weeks for evaluation of response after induction. All patients demonstrated FDG-avidlesions on the baseline PET/CT scan. The metabolic response was assessed according to EORTC criteria and based on the mean difference in SUVmax between the two PET/CT scans, and the patients were classified into four groups: complete or partial metabolic response, or stable or progressive metabolic disease (CMR, PMR, SMD and PMD, respectively). All patients were followed in our institution. Results Metastatic sites were localized in bone (n=15), lymph nodes (n=11), chest wall (n=3), breast (n=5), lung (n=3), soft tissue (n=1) and liver (n=1). PMR was observed in 11 patients (50%), SMD in 5 (23%) and PMD in 6 (27%). The median progression-free survival (PFS) times were 20, 27 and 6 months in the PMR, SMD and PMD groups, respectively. PFS in the SMD group differed from that in the PMR and SMD groups (p<0.0001). Conclusion Metabolic response assessed by FDG PET/CT imaging in patients with metastatic breast cancer treated with endocrine therapy is predictive of the patients' PFS.