Abstract P4-11-32: Routine histopathological variables predict oncotype DX risk categories

Abstract

Abstract Background: Oncotype DX(ODX) is a clinically validated, commercially available multi-gene assay that provides prognostic and predictive information in estrogen receptor(ER)-positive, Her2-negative breast cancer. Because health care system does not cover this expensive assay in many countries, physicians and researchers try to use routine histopathological variables predict ODX Recurrence Score (RS). Hyunseok Kim et.al presented at ASCO that Estimated Recurrence Score (ERS) model could identify those patients most likely to benefit from including ODX RS results in therapeutic decision-making (J Clin Oncol 32:5s, 2014 suppl; abstr 559). Methods: We retrospectively reviewed histopathological slides between July 2007 and April 2014 from Toranomon Hospital patients (n=149) with early stage ER-positive, Her2-negative breast cancer, for whom ODX was ordered. We developed an original linear regression model using routine histopathological markers (Allred Score for progesterone receptor (PR), nuclear grade(NG), and Ki67) to calculate an Estimated Recurrence Score (ERS), and correlated it with the observed ODX RS assay result. ERS=20.46+0.298xKi67–1.48xPR+1.41xNG predicts the ODX RS with an R2 of 0.48. In order to internally validate this model in the Toranomon Hospital cohort in Japan, we adapted Hyunseok’s algorithm. Results: 132 patients had an observed RS ≤ 25 (89%) and 17 patients had an observed RS above 25 (11%). When the ERS was < 21 (n=124), we accurately classified 97% of them (120) who were found to have a low risk (observed RS ≤ 25). Similarly, 83% of those (5/6) with an ERS > 30 fell into a high risk category with observed RS > 25. Table1 (TAILORx risk categories)Toranomon cohortODX ≤25ODX RS>25TotalERS < 211204124ERS(21-30)11819ERS(> 30)156Total13217149 We also presented the comparison of ERS and observed RS based on original risk categories. Table2 (Original risk categories )Toranomon cohortODX RS<18ODX RS 18-30ODX RS>30TotalERS(<18)6633099ERS(18-30)1725244ERS(>30)0156Total83597149 Conclusions: We developed an ERS model to find those patients most likely to benefit from ODX RS results in clinical practice setting. Although further external and prospective validation is mandatory, preliminary result supports the usefulness of this ERS model. Citation Format: Hidetaka Kawabata, Keiichi Kinowaki, Nobuko Tamura, Yoko Kobayashi, Masami Kadowaki, Daishu Miura, Toshimi Takano, Akihiko Shimomura, Tsuguo Iwatani, Yuko Kitawaki, Takeshi Fujii. Routine histopathological variables predict oncotype DX risk categories [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-11-32.