The relationship of oncotype Dx Recurrence Score (RS) with Ki 67 in early stage breast cancer patients in a community based cancer center in rural central Nebraska.

Abstract

e12566 Background: Oncotype Dx recurrence score (RS), is a prognostic and predictive test utilized for decision making in adjuvant therapy of 0-3 node/hormone receptor positive(HR+)/ HER-2-negative early breast cancer. Ki-67 is a marker of proliferating cells and is associated with prognosis and response. Immunohistological (IHC) assessment of Ki 67 expression is less expensive and with the approval of CDK inhibitors in the high risk adjuvant setting, it is increasingly being utilized in clinical decision making. A moderate to strong correlation between Ki67 and Oncotype Dx RS has been reported in the literature. We sought to examine the relationship of Ki 67 to Oncotype Dx RS in a community-based cancer center in rural central Nebraska. Methods: Forty-three consecutive postmenopausal breast cancer patients(pts) diagnosed and treated at our community based cancer center between 2020-2021 with T1–2 N0-1 M0, HR+, HER-2-negative disease were evaluated for histological type, tumor size, Nottingham grade, HR levels, Ki 67 expression (low < 10%, intermediate 10 ≥ Ki67 < 25 high ≥ 25), and Oncotype Dx RS(low <16,intermediate 16⩽RS<26), high ⩾26). Ki 67 and Oncotype Dx RS were treated as continuous variables to calculate a Pearson correlation coefficient. Results: Mean age at diagnosis was 59.4 years (range 48-89). Mean tumor diameter was 15.6 mm. 78.9% were intermediate histologic grade and 9.7% patients had lymph node involvement. Median expression of ER and PR were 90% (5-100) and 70% (0-100), respectively. The mean Ki 67 value was 17.5 (range 5-60 %), and mean Oncotype RS was 14.4 (range 4-34). There was a positive linear correlation between Ki 67 expression and Oncotype Dx RS (Pearson Correlation Coefficient=0.49, P-value <0.001). The vast majority of high Ki 67 pts (80%) had high/intermediate Oncotype RS. All pts with low Ki 67 (100%) had low/intermediate RS. Conclusions: Our community based rural cancer center data support a linear, statistically significant, positive correlation between Ki 67 and Oncotype Dx RS in early stage 0-3 node/HR+ positive breast cancer pts. Increasing use of Ki 67 testing in different clinical settings will generate more data to better define this correlation.[Table: see text]