Objective: To investigate the association between the recurrence score (RS) obtained by Oncotype DX 21-gene  test and long non-coding RNA (lncRNA) MALAT1  expression in early and estrogen receptor-positive (ER⁺) breast cancer.
Materials and Methods: The Oncotype DX 21-gene  test and MALAT1  expression detection were performed in tumor samples from 76 ER⁺ and early breast cancer patients with the Surplex liquid chip. The RS value was calculated based on the expression of total 21 genes. The level of MALAT1  was measured in both tumor tissue and para-tumor tissue, and relatively quantified with an internal control gene. Mann–Whitney U -test or Kruskal–Wallis test were used to analyze the association between MALAT1  level and different clinical pathological characteristics, including age, tumor stage, disease grade, lymph node status, Ki-67 expression, and progesterone receptor (PR) status. The association between the RS and different characteristics was analyzed by Wilcoxon rank-sum test. Correlation between two parameters was analyzed by Spearman’s rank correlation analysis.
Results: The expression of MALAT1  was more abundant in tumor tissue (2.992 ± 2.256) than that in adjacent normal tissue (1.641± 1.438, Z =− 2.594, p= 0.009), and it was not correlated with any clinical pathological characteristics. According to the old criteria for RS stratification, 52.7% of patients were in low risk (RS< 18), 36.8% of patients were in medium risk (18≤RS≤ 30), and 10.5% of patients were in high risk (RS> 30). While under the new criteria, 18.4% were in low risk group (RS< 11), 63.2% were in a medium risk group (11≤RS≤ 26), and 18.4% were in a high risk group (RS> 26). The Oncotype DX 21-gene  results only correlated with Ki-67 expression under both new and old criteria, and it was not related with other cancer characteristics. The expression of lncRNA MALAT1  was significantly correlated with the Oncotype DX 21-gene  results under the old criteria.
Conclusion: MALAT1  is a novel breast cancer biomarker independent of tumor stage, disease grade and lymph node status. MALAT1  level is associated with the Oncotype DX 21-gene  RS value. Therefore, combination of MALAT1  and the Oncotype DX 21-gene  test may be used to predict prognosis in ER⁺ and early stage breast cancer.
Keywords: Oncotype DX 21-gene test, MALAT1, long non-coding RNA; lncRNA, breast cancer, risk of recurrence