Abstract P2-02-08: Validation of an autoantibody blood test for the detection of early breast cancer (BC), particularly hormone receptor positive BC

Background: Breast cancer (BC) remains the most common type of cancer in women, with an incidence of 1.6 million cases per year worldwide. Early detection through mammographic screening reduces BC mortality by ˜20%, which while highly significant still leaves 80% of BC deaths unchanged. Furthermore, mammographic screening is only applicable to women between 50-70 years, in which only about one third of BCs occurs. There is an urgent need to identify a test, preferably a blood test showing high sensitivity and specificity for early BC across all ages of patients and all tumour types. Advances in understanding of the human autoantibody (AAB) response to early cancers has allowed us to harness this biological phenomenon for early cancer detection. . Aim: To identify a panel of tumor associated antigens (TAAs) which would detect AABs in the blood with high sensitivity and specificity for early BC: enabling cancer/normal discrimination. Methods: Serum samples from 120 BC patients and matched controls were tested against a panel of 60 multiple TAAs using an optimised new multiplex microarray platform. A sub-group of 60 samples were also tested for AABs to estrogen receptor (ER). The selected TAAs were spotted onto a glass slide surface in an automated, highly reproducible system platform. If serum autoantibodies are present they bind to one or more of the TAA spots. Bound antibodies are detected with a fluorescent reporter and signal intensity measured using GenePix pro-6. Data analysis : A Monte Carlo Simulation method was employed to define the best panel of the antigens with optimised cutoff points in each assay that would yield the highest sensitivity and specificity to discriminate BC patients from controls. AAB positivity in the BC group was analysed by tumor size (≤20mm versus >20mm), histological grade, lymph node status (positive or negative) and ER status (positive or negative) Results: Using a panel of 12 TAAs, AABs were detected in pre-op blood of 34/60 (57%) primary BC patients compared to 9/59 controls (15%) (p=0.000003); one control sample data was unavailable. This gave a sensitivity of 57% and specificity of 85%. Median age of BC patients was 59yrs (20-81) versus 59yrs (28-81) in controls. There was no significant difference for AAB detection when compared to tumour size, grade, lymph node status or ER status. In the sub-group of 60 patients where ER antigen was measured using a panel of 8 TAAs AABs were detected in 20/29 BC patients compared to 2/30 controls (p=3.5e-7). This represents a sensitivity of 69% with a specificity of 93%. Conclusions: These results confirmed our hypothesis that AABs can be detected in women of all ages with early BC. AABs were not related to tumour size, grade, lymph node status or ER status. If a panel of AAB assays can be validated it opens the possibility of a blood test for detection of early BC. Future direction of this research will be i) validation studies of a panel of AABs for detection of early BC, ii) detection of AABs at the earliest stages of carcinogenesis and iii) a panel of AABs which detect ER positive BC thereby enabling stratified chemoprevention in a high risk group combined with mammographic screening. Citation Format: Negm OH, Ahmed O, Figueredo GP, Hamed MR, Pollard L, Garibaldi J, Sewell H, Robertson JF. Validation of an autoantibody blood test for the detection of early breast cancer (BC), particularly hormone receptor positive BC [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-02-08.