In tumor lesions, RGD-based tracer uptake is significantly lower than that of FDG, as commonly observed in studies comparing FDG and RGD tracers (52, 63, 65, 66, 86–92), but this difference was altered in some cases, such as with the higher maximum SUV (SUVmax) and tumor-to-blood ratio (TBR) of 68Ga-NOTA-3P-TATE-RGD compared with 18F-FDG in neuroendocrine tumor (NET) cases and also in both human epidermal growth factor receptor 2 negative [HER2 (–)] and estrogen receptor positive [ER (+)] breast cancer (52, 88). Here, ESR1 is linked to breast cancer.