Radiolabelled Trastuzumab PET/CT imaging: a promising non-invasive tool for the in vivo assessment of HER2 status in breast cancer patients

Purpose: In patients with breast cancer, the overexpression of human epidermal growth factor receptor 2 (HER2) is associated with a worse prognosis and a better response to target therapy with monoclonal antibody, such as trastuzumab. HER2 status is usually revealed by immunohistochemistry (IHC) and/or fluorescence in situ hybridization (FISH) on tumour tissue sample. Recently, PET/CT with radiolabelled trastuzumab has been described as a non-invasive tool for the identification of HER2-positive lesions in patients with BC, with a potential role in the selection of patients candidates to target therapy. The purpose of this mini-review of current literature is to summarize the state of the art of PET/CT imaging with these new radiopharmaceuticals. Methods: PubMed/MEDLINE database was screened to find articles regarding the role of radiolabelled trastuzumab PET/CT in detecting HER2-positive breast cancer lesions. Terms breast cancer AND (PET OR positron emission tomography) AND (trastuzumab OR radiolabelled monoclonal) were used. Results: Fourteen studies exploring the role of radiolabelled trastuzumab PET/CT in BC patients were included. Three different radiopharmaceuticals were used (89Zr-Trastuzumab, 64Cu-Trastuzumab and 68Ga-DOTA-F(abʹ)2-Trastuzumab). Clinical data were not available for all studies and quite heterogeneous within the same studies; methodological aspects were also quite different among studies, while the comparison with conventional imaging techniques was common. Conclusion: Additional studies are needed to validate the potential role of radiolabelled trastuzumab PET/CT, demonstrating its effectiveness in detection of HER2-positive lesions and in identification of BC patients who could benefit from specific and personalized therapy.