Abstract: Background and purpose: The Oncotype DX21 gene assay holds great promise in prognostic prediction and adjuvant treatment decision-making, but the test samples obtained through invasive surgery can not completely represent the whole tumor. Mammography is a noninvasive, economical and simple routine examination. If imaging markers can be found, information about related gene expression quantity can be obtained in a noninvasive way, and the purpose of predicting prognosis and recurrence risk probability can also be achieved. This study explored the correlation between X-ray imaging characteristics and Oncotype DX21 gene assay results ［recurrence score (RS) and RS grades］ in patients with early-stage invasive ductal carcinoma who were ER-positive, HER2-negative and node-negative. Methods: Data of 282 patients with ER-positive, HER2-negative and node-negative early-stage invasive ductal carcinoma who underwent mammography and Oncotype DX21 gene assay in Fudan University Shanghai Cancer Center from Sep. 2017 to Jun. 2019, were retrospectively collected. Univariate and multivariate ordered logistic regression was used to analyze the correlation between X-ray imaging features and RS grading. One-way analysis of variance was used to analyze the correlation between X-ray imaging features and RS scores. Results: Univariate and multivariate ordered logistic regression analysis consistently showed that mass margins and calcification morphology were significantly correlated with RS grading (P<0.05). It was further found that the RS mean value of mass with indistinct margins was 33.6, which was significantly different from circumscribed (18.4), spiculated (24.9), microlobulated (27.3), and obscured margins (23.1). There were also significant differences in the RS mean value between amorphous calcification and punctate calcification. Conclusion: Calcification morphology and mass margins in mammograms have the potential to become imaging markers for Oncotype DX21 gene assay, providing a powerful tool for clinicians to make individualized treatment decisions.

Key words: Invasive ductal carcinoma, Oncotype DX21 gene assay, X-ray imaging features