In addition to the well-known estrogen receptor (ER) and human epidermal growth factor receptor 2, the androgen receptor (AR) is also a potential drug target in breast cancer treatment. Whole-body imaging can provide information across lesions within a patient. ER expression in tumor lesions can be visualized by F-fluoroestradiol (F-FES) PET, and AR expression has been visualized in prostate cancer patients with F-fluorodihydrotestosterone (F-FDHT) PET. Our aim was to assess the concordance between F-FDHT andF-FES PET and tumor AR and ER expression measured immunohistochemically in patients with metastatic breast cancer. Patients with ER-positive metastatic breast cancer were eligible for the study, irrespective of tumor AR status. The concordance ofF-FDHT and F-FES uptake on PET with immunohistochemical expression of AR and ER in biopsies of corresponding metastases was analyzed. Patients underwentF-FDHT PET and F-FES PET. A metastasis was biopsied within 8 wk of the PET procedures. Tumor samples with more than 10% and 1% nuclear tumor cell staining were considered, respectively, AR- and ER-positive. Correlations between PET uptake and semiquantitative immunohistochemical scoring (percentage positive cells × intensity) were calculated. The optimum threshold of SUV to discriminate positive and negative lesions for both AR and ER was determined by receiver-operating-characteristic analysis. In the 13 evaluable patients, correlation ( ) between semiquantitative AR expression and F-FDHT uptake was 0.47 ( = 0.01) and between semiquantitative ER expression and F-FES uptake 0.78 ( = 0.01). The optimal cutoff for AR-positive lesions was an SUV of 1.94 for F-FDHT PET, yielding a sensitivity of 91% and a specificity of 100%; the optimal cutoff was an SUV of 1.54 for F-FES PET, resulting in a sensitivity and specificity of 100% for ER.F-FDHT and F-FES uptake correlate well with AR and ER expression levels in representative biopsies. These results show the potential use of whole-body imaging for receptor status assessment, particularly in view of biopsy-associated sampling errors and heterogeneous receptor expression in breast cancer metastases.
Molecular imaging with radiolabelled targeted anticancer drugs has great potential for the improvement of personalized cancer care. The non-invasive quantification of drug accumulation in tumours and normal tissues provides understanding of the biodistribution in relation to therapeutic and toxic effects.
Purpose: Correct identification of tumour receptor status is important for treatment decisions in breast cancer. [ 18 F]FES PET and [ 18 F]FDHT PET allow non-invasive assessment of the oestrogen (ER) and androgen receptor (AR) status of individual lesions within a patient. Despite standardised analysis techniques, interobserver variability can significantly affect the interpretation of PET results and thus clinical applicability. The purpose of this study was to determine visual and quantitative interobserver variability of [ 18 F]FES PET and [ 18 F]FDHT PET interpretation in patients with metastatic breast cancer. Methods: In this prospective, two-centre study, patients with ER-positive metastatic breast cancer underwent both [ 18 F]FES and [ 18 F]FDHT PET/CT. In total, 120 lesions were identified in 10 patients with either conventional imaging (bone scan or lesions > 1 cm on high-resolution CT, n = 69) or only with [ 18 F]FES and [ 18 F]FDHT PET (n = 51). All lesions were scored visually and quantitatively by two independent observers. A visually PET-positive lesion was defined as uptake above background. For quantification, we used standardised uptake values (SUV): SUV max , SUV peak and SUV mean. Results: Visual analysis showed an absolute positive and negative interobserver agreement for [ 18 F]FES PET of 84% and 83%, respectively (kappa = 0.67, 95% CI 0.48-0.87), and 49% and 74% for [ 18 F]FDHT PET, respectively (kappa = 0.23, 95% CI − 0.04-0.49). Intraclass correlation coefficients (ICC) for quantification of SUV max , SUV peak and SUV mean were 0.98 (95% CI 0.96-0.98), 0.97 (95% CI 0.96-0.98) and 0.89 (95% CI 0.83-0.92) for [ 18 F]FES, and 0.78 (95% CI 0.66-0.85), 0.76 (95% CI 0.63-0.84) and 0.75 (95% CI 0.62-0.84) for [ 18 F]FDHT, respectively.
Positron emission tomography using [18F]fluorodeoxyglucose (FDG PET) potentially underperforms for staging of patients with grade 1–2 estrogen receptor positive (ER+) breast cancer. The aim of this study was to retrospectively investigate the diagnostic accuracy of FDG PET in this patient population. Suspect tumor lesions detected on conventional imaging and FDG PET were confirmed with pathology or follow up. PET-positive lesions were (semi)quantified with standardized uptake values (SUV) and these were correlated with various pathological features, including the histological subtype. Pre-operative imaging detected 155 pathologically verified lesions (in 74 patients). A total of 115/155 (74.2%) lesions identified on FDG PET were classified as true positive, i.e., malignant (in 67 patients) and 17/155 (10.8%) lesions as false positive, i.e., benign (in 9 patients); 7/155 (4.5%) as false negative (in 7 patients) and 16/155 (10.3%) as true negative (in 14 patients). FDG PET incorrectly staged 16/70 (22.9%) patients. The FDG uptake correlated with histological subtype, showing higher uptake in ductal carcinoma, compared to lobular carcinoma (p < 0.05). Conclusion: Within this study, FDG PET inadequately staged 22.9% of grade 1–2, ER + BC cases. Incorrect staging can lead to inappropriate treatment choices, potentially affecting survival and quality of life. Prospective studies investigating novel radiotracers are urgently needed.
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