Patients with newly diagnosed or suspected breast cancer will undergo one [68Ga]Ga-TTP scan and one [18F]FDG scan within 1 week, in randomized order, with no anticancer treatment administered between the two imaging examinations. This cohort is used to evaluate tumor targeting, compare diagnostic performance with [18F]FDG, and correlate imaging findings with pathology and TROP2 expression.

Patients with breast cancer who are planned to receive TROP2-directed ADC therapy will undergo paired [68Ga]Ga-TTP and [18F]FDG imaging at three time points: before treatment, after 2 cycles of ADC therapy(each cycle is 21 days), and at disease progression. This cohort is used to assess longitudinal imaging changes and their relationship with treatment response.

[18F]FDG is administered intravenously as the comparator PET radiotracer. In the diagnostic validation cohort, participants undergo one [18F]FDG PET examination within 1 week of the [68Ga]Ga-TTP scan, with no treatment between scans. In the ADC response assessment cohort, participants undergo [18F]FDG PET imaging at the same three time points as [68Ga]Ga-TTP: before ADC therapy, after 2 cycles(each cycle is 21 days), and at disease progression. The planned administered activity is approximately 0.1-0.15 mCi/kg.

To compare the diagnostic performance of [68Ga]Ga-TTP PET and [18F]FDG PET for breast cancer lesions, including sensitivity, specificity, accuracy, false-positive rate, and false-negative rate, using pathology and/or integrated follow-up assessment as reference standard.

To evaluate the association between changes in tumor uptake on [68Ga]Ga-TTP PET (e.g., SUV or SUVmax) before treatment, after 2 cycles of TROP2-directed ADC therapy(each cycle is 21 days), and at disease progression, and clinical treatment response in patients with breast cancer receiving ADC therapy.assessed up to 24 months.

To evaluate the correlation between standardized uptake values of [68Ga]Ga-TTP PET in target or suspected tumor lesions and TROP2 expression level in corresponding pathological tissue samples.