Whole-body PET/CT predicts response to HER2-targeted therapy in metastatic breast cancer patients

Reston, VA—A new imaging agent, ⁶⁸Ga-ABY-025, can predict early metabolic response to human epidermal growth factor receptor 2 (HER2)-targeted treatment in HER2-positive metastatic breast cancer patients, according to new research published in the September issue of The Journal of Nuclear Medicine. By providing whole-body quantification of HER2 expression, ⁶⁸Ga-ABY-025 PET/CT can play a valuable role in treatment planning and could spare patients from unnecessary drug-related side effects. 

Up to 20 percent of breast cancer patients have HER2 overexpression, making HER2 an attractive therapy target for both new and recurring cases. However, since breast cancer is a heterogeneous disease and HER2 expression may vary within the same patient and over time, HER2-targeted treatment failure is common, and cure remains rare in metastatic disease.

“While HER2 status can be confirmed by biopsy results in early-stage breast cancer, it is more complicated in advanced disease where multiple metastases might have a heterogeneous HER2 expression,” said Ali Alhuseinalkhudhur, MD, PhD candidate in the Department of Immunology, Genetics, and Pathology at Uppsala University in Uppsala, Sweden. “Imaging the entire body rather than just the primary cancer site can give physicians a total estimate of HER2 expression so they can plan targeted therapies appropriately.”

Researchers investigated ⁶⁸Ga-ABY-025 PET as a noninvasive tool for whole-body HER2-receptor quantification. Forty patients with known positive HER2 status were included in the study: 19 with primary breast cancer and 21 with metastatic breast cancer (median of three previous treatments).

⁶⁸Ga-ABY-025 PET/CT, ¹⁸F-FDG PET/CT, and core-needle biopsies from targeted lesions were performed at the baseline for each patient. ¹⁸F-FDG PET/CT was repeated after two cycles of therapy to calculate the directional change in tumor lesion glycolysis. Tracer uptake was measured in up to five of the largest lesions per patient, including the biopsied lesion. Standardized uptake values from ⁶⁸Ga-ABY-025 PET/CT were then compared with the biopsied HER2 status and change in tumor lesion glycolysis.

⁶⁸Ga-ABY-025 PET/CT successfully enabled quantification of HER2 expression, and uptake correlated significantly with metabolic response among patients, particularly in those with metastatic breast cancer. Also, an inverse association was found between the number of previous treatments and the metabolic response to the current treatment; the more treatments received, the higher the ⁶⁸Ga-ABY-025 required to induce a metabolic response.

“The ability of ⁶⁸Ga-ABY-025 PET/CT to provide a whole-body visualization of HER2 expression and to predict metabolic response is advantageous and exceeded the biopsy-based approach for metastatic breast cancer patients,” noted Alhuseinalkhudhur. “HER2-based imaging tools might provide a solution in situations where biopsies cannot be performed safely or when biopsy results are inconsistent. In addition, a PET-based approach to evaluate the appropriateness of targeted therapy might help avoid unnecessary side effects and might provide a more personalized opportunity for timely therapy corrections.”

He continued, “Our work is a strong example of the development toward personalized medicine. We hope that the value of quantification of biomarkers such as HER2 expression in cancer patients will be appreciated to a larger extent and introduced into nuclear medicine practice for both diagnostic imaging and therapy.”   

This study was made available online in July 2023.

The authors of “Human Epidermal Growth Factor Receptor 2–Targeting [⁶⁸Ga]Ga-ABY-025 PET/CT Predicts Early Metabolic Response in Metastatic Breast Cancer” include Ali Alhuseinalkhudhur, Division of Nuclear Medicine and PET, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden, and Department of Immunology, Genetics, and Pathology, Uppsala University, Uppsala, Sweden; Henrik Lindman and Vladimir Tolmachev, Department of Immunology, Genetics, and Pathology, Uppsala University, Uppsala, Sweden; Per Liss, Division of Radiology, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden; Tora Sundin, Clinical Research and Development Unit, Uppsala University Hospital, Uppsala, Sweden; Fredrik Y. Frejd, Department of Immunology, Genetics, and Pathology, Uppsala University, Uppsala, Sweden, and Affibody AB, Solna, Sweden; Johan Hartman and Caroline Rönnlund, Department of Oncology–Pathology, Karolinska Institute, Stockholm, Sweden, and Department of Clinical Pathology and Cancer Diagnostics, Karolinska University Hospital, Stockholm, Sweden; Victor Iyer, Irina Velikyan, and Jens Sörensen, Division of Nuclear Medicine and PET, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden; Joachim Feldwisch, Affibody AB, Solna, Sweden; and Mark Lubberink, Division of Nuclear Medicine and PET, Department of Surgical Sciences, Uppsala University, Uppsala, Sweden, and Department of Medical Physics, Uppsala University Hospital, Uppsala, Sweden.

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