The Use of the [99mTc]Tc-DARPinG3 in Assessing Tumor Process in a Patient with Metastatic HER2-Positive Breast Cancer (Clinical Case Report)

Abstract

Introduction. Although rapid technological progress has improved the diagnosis of oncological diseases, there is still a need to develop methods that not only simultaneously assess the anatomical location of tumor foci (including primary tumor nodes, regional and distant metastases) but also determine their molecular characteristics. One such technique currently under active investigation involves targeted radionuclide imaging based on the antigen-antibody reaction. This technique allows to evaluate the binding of a radiopharmaceutical compound to a target antigen on the surface of tumor cells and simultaneously visualize tumor foci in the body of patients by intravenous administration of a finished radiopharmaceutical. Aim. To clinically demonstrate the feasibility of assessing the TNM staging in a patient with metastatic HER2-positive breast cancer using the [^99mTc]Tc-DARPinG3 radiopharmaceutical prior to the initiation of systemic treatment.

Observation. Patient L., 61 years old, in 2020, presented to the outpatient department of the Cancer Research Institute at the Tomsk National Research Medical Center for examination regarding the enlargement and edema of the right breast. Histological and immunohistochemical studies of the biopsy material of the primary tumor and metastatic axillary lymph node revealed data for invasive G2 carcinoma with ER 0, RP 0, HER2/neu 3+ and Ki-67 about 30 %. Results. According to the study using the [^99mTc]Tc-DARPinG3, in addition to the accumulation of the radiopharmaceutical in the projection of breast (SUV_max = 3.1) and in the right axillary, pectoral, supra- and infraclavian lymph nodes (SUV_max = 8.8), the compound accumulation was visualized in the projection of the right parietal bone (SUV_max = 2.01), left greater wing of the sphenoid bone (SUV_max = 4.45), C3 vertebral body (SUV_max = 3.2), right humerus (SUV_max = 1.73), lower third of the sternum (SUV_max = 3.26), body of the right ilium (SUV_max = 2.88), as well as multiple (more than 10) sites in the liver (SUV_max = 8.61). The obtained data were comparable with the results of ultrasound examination of the breast, regional lymph nodes, and liver, as well as CT of the head and neck, thoracic and abdominal cavities, and pelvic bones.

Conclusion. The results demonstrated in this clinical case using the [^99mTc]Tc-DARPinG3 have shown its effectiveness in relation to simultaneous visualization of metastatic foci, as well as in assessing the HER2/neu receptor status in the primary tumor and metastatic axillary lymph nodes.