Abstract P6-09-31: Study of oncotype DX® recurrent score in bilateral synchronous primary invasive breast cancer

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Abstract Background: The 21-gene Oncotype Dx® Recurrence Score (RS) is routinely used to assess the risk of distant recurrence and benefit for adding chemotherapy in the treatment of ER positive HER2 negative early stage breast cancer. Among patients diagnosed with bilateral primary breast cancer there is limited information on the utilization of RS for each primary cancer. In this study, we evaluate the concordance of RS in bilateral breast cancer, and the value of testing both primary cancers in patients diagnosed with synchronous bilateral breast cancer Materials & Methods: This is an IRB approved retrospective study. From 2007 to present, we identified 158 patients with synchronous (within 6 months) bilateral primary breast cancer in our Institutional databases. In this dataset, there were 36 patients who had early stage ER positive, and Her-2 negative bilateral invasive cancer, and for whom the 21-gene Oncotype Dx® RS test was ordered. We excluded patients with bilateral invasive cancer who did not have Oncotype Dx® RS test performed (n=20), patients with bilateral in-situ cancers (n=15), patients with unilateral invasive with contralateral in-situ cancer (n= 64), and patients with locally advanced stage of one or both primary invasive cancers (n=23). In this study, RS score was scored low risk < 18, intermediate 18-30, and high risk >31. The RS for bilateral primary cancers was noted as concordant if the 2 values were in the same risk category and discordant when 2 values represented different risk category. Results: Among the 36 patients, 19 patients had Oncotype Dx® RS tested for one primary cancer, and 17 patients had testing from bilateral primary cancers. Patients median age is 55 years (range: 44 years to 75 years), and invasive duct cell was the most common histology. The RS distribution of low risk, intermediate risk and high risk was 60 %, 30% and 10%, respectively. Further, evaluation of the 17 patients in whom the RS score from bilateral invasive breast cancers was obtained, we noted that the RS was concordant in 11 patients (64.7%), and discordant in 6 patients (35.3%). In 4/6 patients the discordance was between low and intermediate risk, and in 2/6 patients it was between low and high risk. Clinical variables including age, histology, receptor positivity, and grade were not predictive of the rate of RS concordance between the 2 primary cancers. Conclusion: The significant rate of discordance observed in our study suggests that the 21-gene RS for each invasive primary breast cancer should be routinely obtained in patients presenting with bilateral breast cancers. Albeit synchronous events, the individual risk assessment of each primary cancer would help guide risk-tailored personalized cancer treatment. Citation Format: Chadha J, Goel A, Wallach J, Shao T, Klein P, Malamud S. Study of oncotype DX® recurrent score in bilateral synchronous primary invasive breast cancer [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 P6-09-31.