Intra-image referencing for simplified assessment of HER2-expression in breast cancer metastases using the Affibody molecule ABY-025 with PET and SPECT

Dan Sandberg, Vladimir Tolmachev, Irina Velikyan, Helena Olofsson, Anders Wennborg, Joachim Feldwisch, Jörgen Carlsson, Henrik Lindman, Jens Sörensen

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)

Abstract

Purpose: In phase I/II-studies radiolabelled ABY-025 Affibody molecules identified human epidermal growth factor receptor 2 (HER2) expression in breast cancer metastases using PET and SPECT imaging. Here, we wanted to investigate the utility of a simple intra-image normalization using tumour-to-reference tissue-ratio (T/R) as a HER2 status discrimination strategy to overcome potential issues related to cross-calibration of scanning devices. Methods: Twenty-three women with pre-diagnosed HER2-positive/negative metastasized breast cancer were scanned with [111In]-ABY-025 SPECT/CT (n = 7) or [68Ga]-ABY-025 PET/CT (n = 16). Uptake was measured in all metastases and in normal spleen, lung, liver, muscle, and blood pool. Normal tissue uptake variation and T/R-ratios were established for various time points and for two different doses of injected peptide from a total of 94 whole-body image acquisitions. Immunohistochemistry (IHC) was used to verify HER2 expression in 28 biopsied metastases. T/R-ratios were compared to IHC findings to establish the best reference tissue for each modality and each imaging time-point. The impact of shed HER2 in serum was investigated. Results: Spleen was the best reference tissue across modalities, followed by blood pool and lung. Spleen-T/R was highly correlated to PET SUV in metastases after 2 h (r = 0.96, P < 0.001) and reached an accuracy of 100% for discriminating IHC HER2-positive and negative metastases at 4 h (PET) and 24 h (SPECT) after injection. In a single case, shed HER2 resulted in intense tracer retention in blood. In the remaining patients shed HER2 was elevated, but without significant impact on ABY-025 biodistribution. Conclusion: T/R-ratios using spleen as reference tissue accurately quantify HER2 expression with radiolabelled ABY-025 imaging in breast cancer metastases with SPECT and PET. Tracer binding to shed HER2 in serum might affect quantification in the extreme case.

Original languageEnglish
Pages (from-to)1337-1346
Number of pages10
JournalEuropean Journal of Nuclear Medicine and Molecular Imaging
Volume44
Issue number8
DOIs
Publication statusPublished - 1 Aug 2017
Externally publishedYes

Keywords

  • Affibody
  • HER2-receptor
  • PET
  • Shedding
  • SPECT
  • T/R

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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