Molecular Imaging of Biomarkers in Breast Cancer

Abstract

The success of breast cancer therapy is ultimately defined by clinical endpoints such as survival. It is valuable to have biomarkers that can predict the most efficacious therapies or measure response to therapy early in the course of treatment. Molecular imaging has a promising role in complementing and overcoming some of the limitations of traditional biomarkers by providing the ability to perform noninvasive, repeatable whole-body assessments. The potential advantages of imaging biomarkers are obvious and initial clinical studies have been promising, but proof of clinical utility still requires prospective multicenter clinical trials.

Keywords: 18F-FDG; PET/CT; biomarkers; breast; breast cancer; molecular imaging; oncology.

FIGURE 1

41-y-old woman with primary ER-positive, HER2-negative invasive ductal breast carcinoma. Axial CT (A) and fused ¹⁸F-FDG PET/CT (B) images from first examination demonstrate ¹⁸F-FDG–avid osseous foci (arrow) without CT correlates. Biopsy demonstrated osseous metastases. After systemic therapy, axial CT (C) and fused ¹⁸F-FDG PET/CT (D) images demonstrated resolution of ¹⁸F-avid foci but revealed new sclerotic osseous lesions on CT (arrow). Without ¹⁸F-FDG PET, new sclerotic lesions could be mistaken for new osseous metastases, but inclusion of ¹⁸F-FDG PET indicated that new sclerotic lesions are consistent with treated disease.

FIGURE 2

52-y-old woman with metastatic ER-negative, HER2-positive breast cancer. (A) ¹⁸F-FDG maximum-intensity-projection image demonstrates ¹⁸F-FDG–avid malignancy (arrows) in left neck, axilla, and chest wall, as well as focus in L2 vertebra. (B) After 8 wk of systemic therapy with paclitaxel, trastuzumab, and pertuzumab, these lesions resolved, but new ¹⁸F-FDG–avid mediastinal and right axillary nodes appeared (arrows), which were biopsy-proven to be new metastases. Combination of both decreasing and new lesions after therapy is example of metabolic mixed response, which is common in metastatic breast cancer and suggests tumor inhomogeneity.

FIGURE 3

67-y-old woman with ER-positive, HER2-negative metastatic breast cancer. Initial sagittal CT (A) and fused ¹⁸F-FES PET/CT (B) images demonstrate multifocal ¹⁸F-FES–avid osseous metastases. ¹⁸F-FES in liver and bowel is physiologic. (C and D) After therapy with novel ER antagonist and degrader GDC-0810, ¹⁸F-FES avidity in osseous metastases resolves, demonstrating ER engagement and abolished ER availability.