Abstract PS6-15: Mammaprint risk stratification associated with presence of circulating tumor cells in breast cancer

Background: We previously reported the prognostic and predictive value of circulating tumor cells (CTCs) in early and late-stage breast cancer (BC). While the evaluation of CTCs via liquid biopsy in oncology practice guidelines is still evolving, other biomarkers are more commonly used, including multigene sequencing. The 21-gene Oncotype DX (ODX) assay predicts a risk of disease recurrence in patients with estrogen receptor (ER)-positive disease. The 70-gene MammaPrint (MP) panel, on the other hand, predicts a risk of early metastasis, and was developed using ER- and ER+ samples. We sought to understand whether these genomic assays predicted the presence of CTCs. Methods: A cohort of patients with BC and CTC data (i.e. positive or negative) was identified in this retrospective study using the National Cancer Database (NCDB) 2004-2016 registry. Clinicopathologic characteristics, including ODX and MP data, were described using frequencies/proportions. At the univariate level, chi-squared tests were used to evaluate for an association between the results of ODX (low-risk as recurrence score of 25), or MP (low or high risk), and the presence of CTCs. These variables were then assessed at the multivariate level using multiple logistic regression, controlling for other variables we previously showed predicted CTCs, including: race, receptor status, histology and AJCC clinical disease stage. Analyses were performed using SPSS version 26.0. Results: A total of n=4577 patients were evaluated for CTCs: n=940 (20.5%) of which underwent ODX testing, while n=282 (6.2%) underwent MP. Chi-squared analyses showed no association between ODX risk categories and the presence of CTCs (p=0.204), but a significant association between MP and CTCs (p=0.005). Through multivariate analysis, we found the association between a high-risk designation as per MP and the presence of CTCs remained significant (OR 2.65, 95% CI 1.23-5.70, p=0.013), even after controlling for race, receptor status, histology, and AJCC clinical disease stage. A similar multivariate model including ODX as a predictor of CTCs confirmed non-significance (p=0.664). Of patients with MP and CTC data, the majority were 50-70 years of age (n=164, 58.2%), White (n=244, 88.1%), with ductal carcinoma (n=211, 74.8%) on histological evaluation (Table 1). N=12 (4.6%) were diagnosed at stage 0, n=173 (66.0%) at stage I, n=63 (24.0%) at stage II, n=7 (2.7%) at stage III, and n=7 (2.7%) at stage IV. Most were hormone receptor-positive (HR+) and HER2-negative (HER2-) (n=234, 86.3%); n=11 (4.1%) were HR+/HER2+, n=5 (1.8%) were HR-/HER2, while n=21 (7.7%) were triple-negative breast cancers (TNBC). N=62 (22.0%) were assigned high-risk as per MP, while n=220 (78.0%) were assigned low-risk. Conclusion: High-risk of early metastasis, per MammaPrint, was significantly associated with the presence of CTCs. However, a significant association was not observed between Oncotype DX risk stratification and CTCs. This may suggest clinical utility in combining ODX metrics with liquid biopsy in order to maximize survival prognostication, when ODX is utilized as the biomarker. Further evaluation will be required to understand if the MP assay’s clinical value contribution is independent of CTC status. Citation Format: Nadeem Bilani, Leah Elson, Hong Liang, Elizabeth Elimimian, Zeina Nahleh. Mammaprint risk stratification associated with presence of circulating tumor cells in breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-15.