¹⁸F-FDG PET/CT for Monitoring of Treatment Response in Breast Cancer

Abstract

Changes in tumor metabolic activity have been shown to be an early indicator of treatment effectiveness for breast cancer, mainly in the neoadjuvant setting. The histopathologic response at the completion of chemotherapy has been used as the reference standard for assessment of the accuracy of 18F-FDG PET in predicting a response during systemic treatment. Although a pathologic complete response (pCR) remains an important positive prognostic factor for an individual patient, a recent metaanalysis could validate pCR as a surrogate marker for patient outcomes only in aggressive breast cancer subtypes. For establishment of the clinical application of metabolic treatment response studies, larger series of specific breast cancer subtypes—including hormone receptor–positive, human epidermal growth factor receptor 2–positive, and triple-negative breast cancers—are necessary. In addition, thresholds for relative changes in 18F-FDG uptake to distinguish between responding and nonresponding tumors need to be validated for different systemic treatment approaches, with progression-free survival and overall survival as references. A PET-based treatment stratification is applicable clinically only if valid alternative therapies are available. Of note, patients who do not achieve a pCR might still benefit from neoadjuvant therapy enabling breast-conserving surgery. In the metastatic setting, residual tumor metabolic activity after the initiation of systemic therapy is an indicator of active disease, whereas a complete resolution of metabolic activity is predictive of a successful treatment response.

Imaging Considerations and Interprofessional Opportunities in the Care of Breast Cancer Patients in the Neoadjuvant Setting

“…47,49,88 18 F-FDG-PET/CT evaluation of NAT response has yet to gain wide acceptance due to limited accuracy and specificity of the technique; these limitations have been attributed to significant differences in 18 F-FDG uptake between breast cancer subtypes, both at baseline and after treatment. 48–50,88 While the ability of 18 F-FDG-PET/CT to predict NAT response may be receptor status dependent and requires further investigation, the technique shows promise for early evaluation and prediction of response to NAT prior to downstream alterations in tumor size. Figure 2 reveals how quantitatively assessing treatment response with 18 F-FDG-PET imaging during NAT can provide indications of response.…”

Semiquantitative Parameters in PSMA-Targeted PET Imaging with 18F-DCFPyL: Variability in Normal-Organ Uptake

“…18 F-FDG PET/CT, in particular, has emerged as a useful approach to the assessment of metabolic response in a variety of tumors, partly on the basis of its ability to quantify radiotracer uptake within tumors and quantitatively determine response to therapy (15)(16)(17)(18). These characteristics of PET offer significant advantages over anatomic imaging, in which size and morphologic changes must be used to judge the presence or absence of disease and response to therapy.…”

Prospective Clinical Trial of 18F-Fluciclovine PET/CT for Determining the Response to Neoadjuvant Therapy in Invasive Ductal and Invasive Lobular Breast Cancers

“…However, the detection of malignancy and the evaluation of a tumor response are separate tasks. Changes in 18 F-FDG avidity have been extensively proven to correlate with the tumor response in breast cancer and many other malignancies (24)(25)(26)(27). This prospective clinical trial provided evidence that changes in 18 F-fluciclovine avidity also correlate well with the tumor response in patients with breast cancer (Spearman r, 0.79; P , 0.001).…”