Possibilities of predicting the HER2 / neu status in a primary tumor in breast cancer patients using ^99mTc-DARPinG3

Aim. To determine informative prognostic criteria for assessing the HER2 / neu status in primary breast cancer using 99mTc-DARPinG3.

Materials and methods. The study included 10 patients with breast cancer (T1-4N0-2M0) before systemic therapy, who underwent a radionuclide study using 99mTc-DARPinG3 at a dose of 3,000 μg. Five patients were characterized by HER2 / neu overexpression in primary breast cancer, whereas 5 patients were HER2-negative. For all patients, morphological and immunohistochemical studies and fluorescence in situ hybridization (FISH) of the primary tumor nodule were carried out. Single-photon emission computed tomography (SPECT) of the chest was performed for all patients 4 hours after the injection of 99mTc-DARPinG3.

Results. The total activity of 99mTc-DARPinG3 was 522.4 ± 341.8 MBq. The comparative analysis showed that higher uptake of the labeled protein in HER2-positive breast cancer was significant (p = 0.0159, Mann – Whitney U test). The analysis of the ratios showed significant differences in the tumor-to-background ratios in patients with HER2-positive breast cancer (p < 0.0159, Mann – Whitney U test). Based on the logistic regression analysis, a mathematical model was developed to predict the status of HER2 / neu in primary breast cancer patients (specificity and sensitivity 100%; p = 0.0004) using 99mTc-DARPinG3 at a dose of 3,000 mcg 4 hours after the injection of the radiopharmaceutical.

Conclusion. The results of the study allow to consider the tumor-to-background ratio 4 hours after the injection of 99mTc-DARPinG3 as an additional prognostic parameter for determining the HER2 / neu status in primary breast cancer.

Clinical possibilities of HER2-positive breast cancer diagnosis using alternative scaffold proteins

HER2-positive breast cancer occurs in 15–20% of breast cancer patients and is associated primarily with a poor prognosis of the disease and the need for highly specific targeted therapy. Despite the clinical importance of determining HER2/neu, traditional diagnostic methods have their disadvantages and require the study of new additional research techniques.

The information presented in this review makes it possible to consider current trends in the radionuclide diagnosis of HER2-positive breast cancer using the latest class of alternative scaffold proteins and to consider various aspects of their use in clinical practice.

The Evolution of Targeted Radionuclide Diagnosis of HER2-Positive Breast Cancer

This review examines the evolution of the radionuclide diagnosis of HER2-positive breast cancer using various compounds as a targeting module in clinical practice: from full-length antibodies to a new group of small synthetic proteins called alternative scaffold proteins. This topic is of especial relevance today in view of the problems attendant to the detection of breast cancer with HER2/neu overexpression, which, in most cases, introduce errors in the treatment of patients. The results of clinical studies of radiopharmaceuticals based on affibody molecules, ADAPTs, and DARPins for SPECT and PET have demonstrated good tolerability of the compounds, their rapid excretion from the body, and the possibility to differentiate tumor sites depending on the HER2/neu status. This indicates that targeted radionuclide diagnosis holds promise and the need to continue research in this direction.