Traditional imaging often misses lobular breast cancer because these cells do not form solid tumors and float freely, making them hard to detect with scans that rely on tumor size or glucose metabolism. FES-PET/CT offers a better alternative by targeting estrogen receptors (ER), which lobular cancer cells depend on.
Compared with standard FDG-PET/CT, which uses glucose as a tracer and detects metabolic activity, FES-PET/CT uses estradiol to detect ER-positive cells. This gives it a much higher sensitivity—around 90% versus 45–50% for standard imaging.
FES-PET/CT is most useful for specific clinical questions rather than routine monitoring. It can accurately detect distant metastases, predict response to hormone therapy (an SUVmax ≥1.8 indicates likely benefit), and provide biomarker information in areas difficult to biopsy, like bone or brain. It can also clarify cases with low ER expression to guide treatment decisions. However, it is not suitable for initial diagnosis or staging of local lymph nodes, and current NCCN Guidelines recommend its use mainly for suspected metastatic lobular or ER-positive breast cancers.