Molecular Imaging of HER2 Expression in HER2-positive Breast Cancer Using 99mTc-ADAPT6 vs 99mTc-DARPinG3

Inclusion Criteria:

1. Subject is \> 18 years of age;
2. Diagnosis of primary breast cancer with possible lymph node metastases before system (chemo+targeted therapy);
3. Availability of results from HER2 status previously determined on material from the primary tumor: HER2-positive, defined as a DAKO HercepTest™ score of 3+ or FISH positive;
4. Sequential injection of 99mTc-ADAPT6 and 99mTc-DARPinG3 in the interval of 3-4 days in each HER2-positive breast cancer patient;
5. Hematological, liver and renal function test results within the following limits:

   * White blood cell count: \> 2.0 x 109/L
   * Hemoglobin: \> 80 g/L
   * Platelets: \> 50.0 x 109/L
   * ALT, ALP, AST: =\< 5.0 times Upper Limit of Normal
   * Bilirubin =\< 2.0 times Upper Limit of Normal
   * Serum creatinine: Within Normal Limits
6. A negative pregnancy test for all patients of childbearing potential. Sexually active women of childbearing potential participating in the study must use a medically acceptable form of contraception for at least 30 days after study termination;
7. Subject is capable to undergo the diagnostic investigations to be performed in the study;
8. Informed consent

Exclusion Criteria:

1\. Second, non-breast malignancy 2. Active current autoimmune disease or history of autoimmune disease 3. Active infection or history of severe infection within the previous 3 months (if clinically relevant at screening) 4. Known HIV positive or chronically active hepatitis B or C 5. Administration of other investigational medicinal product within 30 days of screening 6. Ongoing toxicity \> grade 2 from previous standard or investigational therapies, according to US National Cancer Institute's

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