摘要Objective:This study aimed to evaluate the clinical utility of[68Ga]Ga-RM2 positron emission tomography/computed tomography(PET/CT),in comparison with 18F-fluorodeoxyglucose([18F]FDG)PET/CT,for staging and prognosis in patients with estrogen receptor-positive(ER+)breast cancer.Methods:This prospective study enrolled nine female patients with breast cancer(mean age 45.5±11.5 years).Eight patients were confirmed to have ER+disease.All participant underwent both[68Ga]Ga-RM2 PET/CT and[18F]FDG PET/CT scans within a one-week interval.The maximum standardized uptake values(SUVmax)was measured for primary tumors,lymph nodes,and metastatic lesions.The physiological distribution of[68Ga]Ga-RM2 was also evaluated.Results:No adverse events were observed.Metastatic were identified in lymph nodes(n=29 lesions),bone(n=19),liver(n=7),brain(n=3),and multiple other sites.[68Ga]Ga-RM2 demonstrated a significantly higher median SUVmax than[18F]FDG across all lesions[7.5(interquartile range,IQR,3.4-14.0)vs.4.0(IQR,2.3-6.1);P<0.001].Similarly,the tumor-to-background ratio(TBR)was significantly superior with[68Ga]Ga-RM2 for all type of lesions:primary tumors[12.3(IQR,10.4-18.3)vs.7.0(IQR,6.0-10.0);P<0.001],lymph node metastases[17.8(IQR,4.4-39.0)vs.4.7(IQR,2.7-10.2);P<0.001],hepatic metastases[5.4(IQR,3.7-8.3)vs.1.0(IQR,0.9-1.5);P<0.001],and osseous metastases[13.9(IQR,7.3-18.0)vs.4.3(IQR,1.6-5.9);P<0.001].Physiological uptake of[68Ga]Ga-RM2 was the highest in the pancreas(SUVmax,77.82±22.64),with moderate uptake in the kidneys(2.82±0.62),heart(1.83±0.29),and liver(1.33±0.41).Conclusions:[68Ga]Ga-RM2 PET/CT demonstrates superior uptake metrics for the detection of metastatic lesions,particularly in the brain and breast,suggesting its potential as a valuable complementary imaging modality to[18F]FDG PET/CT.These promising foundings warrant further validation in larger cohorts to confirm their clinical impact and to standardize imaging protocols.