Abstract P2-05-36: Clinicopathological predictors for low risk recurrence distinguished by 21-gene recurrence score in estrogen receptor-positive invasive breast cancer patients

Abstract

Abstract Background: The 21-gene Recurrence Score (RS) (Oncotype DX®; Genomic Health, Redwood City, CA) is the most valid and reliable multigene assay to predict prognosis or response to treatment in hormone receptor-positive invasive breast cancer patients. However, in Japan, the test is expensive (about 4,000 US dollars) and one of the problems is that about 30% of patients will be categorized as having moderate recurrence risk. If clinicopathologic factors can be used to predict patients with low recurrence, many patients can avoid postoperative chemotherapy without testing the RS. Such predictors shall have a substantial impact on medical economics too. The aim of this study was to determine significant clinicopathological predictors for low recurrence risk by RS in patients with estrogen receptor-positive primary breast cancer. Methods: Retrospective cross-sectional study was conducted in tertiary referral hospital in Tokyo, Japan. Two hundreds twenty patients with estrogen receptor-positive invasive breast cancer underwent surgery for breast cancer and tested for RS from November 2009 to March 2016. RS £18 was defined as low recurrence risk. The patients were divided into 2 groups, patients with low recurrence risk (n=143) and with a moderate/high recurrence risk (n=77). Age, menopausal status, histologic type (invasive ductal vs. lobular carcinoma), nuclear grade, progesterone receptor (PR) expression, Ki67 index, tumor size, lymph node status, and lymphovascular invasion were considered as candidate predictors. Student's t test or Wilcoxon-Rank Sum test and Fisher's exact test was used for continuous variables and proportion, respectively. Simple and multiple logistic regression model were used to determine significant predictors. Classification and regression tree analysis (CART) was also conducted. Results: Mean age (SD) of low and moderate/high recurrence patients was 53 years-old (9.4) and 55 years (10.2), respectively. Univariate analyses revealed that the invasive lobular carcinoma, the high PR expression, Ki67 < 24, and the absence of lymphovascular invasion were significantly associated with low recurrence risk. According to multiple logistic regression, The odds ratio (OR) [95%CI] of histological type (invasive lobular), high PR expression, Ki67 < 24, and the absence of lymphovascular invasion was 0.43 [0.08-1.8], 10 [5.4-23.6], 0.95 [0.93-0.97], and 0.57 [0.23-1.18], respectively. The area under the receiver operating characteristic curve was 0.83. CART showed that the probability of low recurrence risk was 79% if with high PR expression, and 92% if with high PR expression and Ki67 < 24. Conclusions: High PR expression and Ki67 < 24 were significant predictors for low recurrence risk by RS in estrogen receptor-positive invasive breast cancer patients. More than 90% of patients with high PR expression and Ki67 < 24 could be classified as low recurrence risk by RS. Citation Format: Tsuchida Y, Hayashi N, Omata F, Yamauchi H. Clinicopathological predictors for low risk recurrence distinguished by 21-gene recurrence score in estrogen receptor-positive invasive breast cancer patients [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-05-36.