To use the molecular PET radionuclide (Ga-68 or F-18) labelled HER2 Affibody to detect the expression of HER2 in the primary and metastatic lesions in patients with HER2 positive or suspicious positive tumors; to detect the expression heterogeneity of HER2 in the lesions and inter-lesions; to observe the change of HER2 expression in the course of treatment. To provide an approach for screening patients high expression of HER2, efficacy monitoring, drug resistance and early warning of recurrence and metastasis to achieve the individualized antitumor treatment of targeted drugs.

HER2 is an important biomarker and directly influences the treatment effect. The guidelines indicate that only HER2-positive patients are eligible for trastuzumab therapy.HER2 positivity is defined as a HER2 score of 3+ by IHC or FISH. However, gastroscopic biopsies are spatiotemporally limited because of the highly heterogeneous expression of HER2. And this procedure is invasive and may substantially increase the incidence of side effects. Additionally, patients with false-negative HER2 results miss the chance for targeted therapy. Moreover, HER2 status can change during the disease process.Thus, a noninvasive, whole-body, HER2-targeted imaging method may be valuable for choosing patients suitable for anti-HER2 therapy and monitoring the therapeutic efficacy. Direct labeling of HER2 antibodies with radionuclides allows clinicians to monitor HER2-targeted therapy and assists in patient staging. With the feasibility of a long half-life and decay time, positron emission tomography (PET) nuclides, such as 64Cu (T1/2= 12.7 h) and 89Zr (T1/2= 78.4 h), can label trastuzumab for the clinical PET imaging of HER2 in GC and breast cancer. Because of the long half-life of 89Zr, 89Zr-trastuzumab is estimated to produce a dosimetry exposure of 0.5 mSv/MBq (compared with the 0.019 mSv/MBq of 18FDG) in patients. Additionally, imaging needs to be performed several days after injection due to the slow blood clearance of antibodies.

In this study, 68Ga-HER2 Affibody or 18F-HER2 Affibody PET/CT imaging will be performed in patients with HER2-positive tumors to access the potential of 68Ga-HER2 Affibody or 18F-HER2 Affibody PET/CT to screen patients who can benefit from HER2 target treatment.

Inclusion Criteria:

1. Aged > 18 years old; ECOG 0 or 1;
2. Patients with HER2 positive or suspicious positive tumors;
3. Has at least one measurable target lesion according to CT or MRI;
4. Life expectancy ≥ 12 weeks.

Exclusion Criteria:

1. Significant hepatic or renal dysfunction;
2. Is pregnant or ready to pregnant;
3. Cannot keep their states for half an hour;
4. Refused to join the clinical research;
5. Suffering from claustrophobia or other mental disorders;
6. Any other situation that researchers considered it unsuitable to participate in the trial.