Abstract
OBJECTIVE: This study aimed to evaluate the clinical utility of [(68)Ga]Ga-RM2 positron emission tomography/computed tomography (PET/CT), in comparison with (18)F-fluorodeoxyglucose ([(18)F]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 [(68)Ga]Ga-RM2 PET/CT and [(18)F]FDG PET/CT scans within a one-week interval. The maximum standardized uptake values (SUV(max)) was measured for primary tumors, lymph nodes, and metastatic lesions. The physiological distribution of [(68)Ga]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. [(68)Ga]Ga-RM2 demonstrated a significantly higher median SUV(max) than [(18)F]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 [(68)Ga]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 [(68)Ga]Ga-RM2 was the highest in the pancreas (SUV(max), 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: [(68)Ga]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 [(18)F]FDG PET/CT. These promising foundings warrant further validation in larger cohorts to confirm their clinical impact and to standardize imaging protocols.