Abstract 761: Comparison of 18F-Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (18F-FDG PET/CT) and conventional imaging (CI) for locally advanced breast cancer staging: A prospective study from a tertiary hospital cancer centre in the Western Cape South Africa
Authors: Chilwesa Paul Mambwe 
Published: September 2020

Abstract
Background
Breast cancer is the second most common cancer in adults, second to lung cancer, and is the most frequently diagnosed cancer in women globally. In South Africa, breast cancer is the commonest type of cancer affecting women and accounts for 26% of all female cancers, excluding non-melanoma skin cancers. Approximately 40% of patients with locally advanced breast cancer (LABC) will develop metastasis within five years after treatment. The presence or absence of distant metastases is the single most important prognostic factor in these patients, and plays a critical role in determination of appropriate therapy. A limited number of studies conducted in LMICs comparing 18F-FDG PET/CT with conventional imaging (CI) have shown superior accuracy of 18F-FDG PET/CT in the detection of distant metastasis in LABC. However, there remains some uncertainty regarding the diagnostic superiority of 18F-FDG PET/CT compared to CI in LABC in South Africa.
Results
Forty-eight participants were recruited; however, 6 were excluded; 2 because of poor quality 18F-FDG PET/CT scans, 1 because of metaplastic histology, and 3 because they did not complete the investigations for analysis. The final analysed sample consisted of 42 participants.
The mean (±SD) age of the participants was 51.5 (±12.71) years, (Range: 27 to 77 years). The stage at presentation was mainly stage IIIB (54.8), with the majority (52.38%), having clinical T4b disease (skin ulceration, peau d'orange or satellite nodules; or palpable nodal disease (90.48%).
The study aimed to assess the difference in the sensitivity of 18F-FDG PET/CT and CI in detecting metastases in patients with locally advanced invasive ductal carcinoma (IDC) of the breast. 18F-FDG PET/CT was superior to the selected CI (CXR, USG, bone scan) in the detection of distant metastases(p=0.0077), resulting in the upstaging of disease in 21.4% of patients from clinical stage IIIa to stage IIIc, and changed management in 54 % of patients. Of the 5 suspected metastatic sites that were biopsied, only one was positive for malignancy. 18F-FDG PET/CT detected ipsilateral supraclavicular lymphadenopathy in 10 (23.8%) patients, which was clinically detected in only 5 (11.9%) patients. 18F-FDG PET/CT detected internal mammary lymphadenopathy (IMN) in 11 (26.1%) patients, 4 (9.5%) of whom had bilateral IMN. Three of the patients with supraclavicular nodal disease detected on 18F-FDG PET/CT were subjected to a biopsy by multi-disciplinary team (MDT) recommendation, and 2 of these were found to be negative on histopathology and/or cytology. The use of 18F-FDG PET/CT for breast cancer staging is recommended in LABC, with a better accuracy if biopsy of isolated suspected metastatic lesions, to avoid the danger of false positive rates, as this has an impact on treatment decisions.
Conclusion
18F-FDG PET/CT is more accurate than CI for the initial staging of LABC, frequently upstaging clinical disease, and requiring modification of loco-regional management. It provides the convenience of examining the whole body in a single session. Larger multi-centred prospective studies are required to ascertain the significance of isolated solitary lesions on 18F-FDG PET/CT.
Citation Format: Paul Mambwe Chilwesa. Comparison of 18F-Fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (18F-FDG PET/CT) and conventional imaging (CI) for locally advanced breast cancer staging: A prospective study from a tertiary hospital cancer centre in the Western Cape South Africa [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 761.